diff --git a/docs/source/conf.py b/docs/source/conf.py
index 4e33931a..ec8294da 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -4,7 +4,6 @@
 #
 import datetime
 
-
 # -- Project information -----------------------------------------------------
 # ref: https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
 #
diff --git a/repo2docker/__main__.py b/repo2docker/__main__.py
index 2ca17f17..cca1616c 100644
--- a/repo2docker/__main__.py
+++ b/repo2docker/__main__.py
@@ -1,14 +1,15 @@
 import argparse
-import sys
-import os
 import logging
+import os
+import sys
+
+from . import __version__
 from .app import Repo2Docker
 from .engine import BuildError, ImageLoadError
-from . import __version__
 from .utils import (
-    validate_and_generate_port_mapping,
-    is_valid_docker_image_name,
     R2dState,
+    is_valid_docker_image_name,
+    validate_and_generate_port_mapping,
 )
 
 
diff --git a/repo2docker/app.py b/repo2docker/app.py
index 5bee81b4..c62a77d6 100755
--- a/repo2docker/app.py
+++ b/repo2docker/app.py
@@ -7,24 +7,23 @@ Usage:
 
     python -m repo2docker https://github.com/you/your-repo
 """
+import getpass
 import json
-import sys
 import logging
 import os
-import entrypoints
-import getpass
 import shutil
+import sys
 import tempfile
 import time
 from urllib.parse import urlparse
 
+import entrypoints
 import escapism
 from pythonjsonlogger import jsonlogger
-
-from traitlets import Any, Dict, Int, List, Unicode, Bool, default
+from traitlets import Any, Bool, Dict, Int, List, Unicode, default
 from traitlets.config import Application
 
-from . import __version__
+from . import __version__, contentproviders
 from .buildpacks import (
     CondaBuildPack,
     DockerBuildPack,
@@ -36,9 +35,8 @@ from .buildpacks import (
     PythonBuildPack,
     RBuildPack,
 )
-from . import contentproviders
 from .engine import BuildError, ContainerEngineException, ImageLoadError
-from .utils import ByteSpecification, chdir, R2dState
+from .utils import ByteSpecification, R2dState, chdir
 
 
 class Repo2Docker(Application):
diff --git a/repo2docker/buildpacks/__init__.py b/repo2docker/buildpacks/__init__.py
index 10fe89a4..7568000b 100644
--- a/repo2docker/buildpacks/__init__.py
+++ b/repo2docker/buildpacks/__init__.py
@@ -1,10 +1,9 @@
-from .base import BuildPack, BaseImage
-from .python import PythonBuildPack
-from .pipfile import PipfileBuildPack
+from .base import BaseImage, BuildPack
 from .conda import CondaBuildPack
-from .julia import JuliaProjectTomlBuildPack
-from .julia import JuliaRequireBuildPack
 from .docker import DockerBuildPack
+from .julia import JuliaProjectTomlBuildPack, JuliaRequireBuildPack
 from .legacy import LegacyBinderDockerBuildPack
-from .r import RBuildPack
 from .nix import NixBuildPack
+from .pipfile import PipfileBuildPack
+from .python import PythonBuildPack
+from .r import RBuildPack
diff --git a/repo2docker/buildpacks/base.py b/repo2docker/buildpacks/base.py
index 0758afc6..e7c9b537 100644
--- a/repo2docker/buildpacks/base.py
+++ b/repo2docker/buildpacks/base.py
@@ -1,14 +1,15 @@
-import textwrap
-import jinja2
-import tarfile
+import hashlib
 import io
+import logging
 import os
 import re
-import logging
 import string
 import sys
-import hashlib
+import tarfile
+import textwrap
+
 import escapism
+import jinja2
 
 # Only use syntax features supported by Docker 17.09
 TEMPLATE = r"""
diff --git a/repo2docker/buildpacks/conda/__init__.py b/repo2docker/buildpacks/conda/__init__.py
index 8c4426dc..99653177 100644
--- a/repo2docker/buildpacks/conda/__init__.py
+++ b/repo2docker/buildpacks/conda/__init__.py
@@ -5,9 +5,9 @@ from collections.abc import Mapping
 
 from ruamel.yaml import YAML
 
-from ..base import BaseImage
-from .._r_base import rstudio_base_scripts
 from ...utils import is_local_pip_requirement
+from .._r_base import rstudio_base_scripts
+from ..base import BaseImage
 
 # pattern for parsing conda dependency line
 PYTHON_REGEX = re.compile(r"python\s*=+\s*([\d\.]*)")
diff --git a/repo2docker/buildpacks/conda/freeze.py b/repo2docker/buildpacks/conda/freeze.py
index 84475457..7bdb444e 100755
--- a/repo2docker/buildpacks/conda/freeze.py
+++ b/repo2docker/buildpacks/conda/freeze.py
@@ -9,17 +9,16 @@ Usage:
 python freeze.py [3.8]
 """
 
-from argparse import ArgumentParser
-from datetime import datetime
 import os
 import pathlib
 import shutil
-from subprocess import check_call
 import sys
+from argparse import ArgumentParser
+from datetime import datetime
+from subprocess import check_call
 
 from ruamel.yaml import YAML
 
-
 HERE = pathlib.Path(os.path.dirname(os.path.abspath(__file__)))
 
 ENV_FILE = HERE / "environment.yml"
diff --git a/repo2docker/buildpacks/docker.py b/repo2docker/buildpacks/docker.py
index 6d8bd469..6979b830 100644
--- a/repo2docker/buildpacks/docker.py
+++ b/repo2docker/buildpacks/docker.py
@@ -1,7 +1,9 @@
 """Generates a variety of Dockerfiles based on an input matrix
 """
 import os
+
 import docker
+
 from .base import BuildPack
 
 
diff --git a/repo2docker/buildpacks/julia/julia_project.py b/repo2docker/buildpacks/julia/julia_project.py
index e6e191dc..d61e65d1 100644
--- a/repo2docker/buildpacks/julia/julia_project.py
+++ b/repo2docker/buildpacks/julia/julia_project.py
@@ -6,8 +6,8 @@ import requests
 import semver
 import toml
 
-from ..python import PythonBuildPack
 from ...semver import find_semver_match
+from ..python import PythonBuildPack
 
 
 class JuliaProjectTomlBuildPack(PythonBuildPack):
diff --git a/repo2docker/buildpacks/julia/julia_require.py b/repo2docker/buildpacks/julia/julia_require.py
index 075b928e..b2acbcff 100644
--- a/repo2docker/buildpacks/julia/julia_require.py
+++ b/repo2docker/buildpacks/julia/julia_require.py
@@ -2,8 +2,8 @@
 
 import os
 
-from ..python import PythonBuildPack
 from ...semver import parse_version as V
+from ..python import PythonBuildPack
 
 
 class JuliaRequireBuildPack(PythonBuildPack):
diff --git a/repo2docker/buildpacks/nix/__init__.py b/repo2docker/buildpacks/nix/__init__.py
index 4947b92e..73dd81af 100644
--- a/repo2docker/buildpacks/nix/__init__.py
+++ b/repo2docker/buildpacks/nix/__init__.py
@@ -1,7 +1,7 @@
 """BuildPack for nixpkgs environments"""
 import os
 
-from ..base import BuildPack, BaseImage
+from ..base import BaseImage, BuildPack
 
 
 class NixBuildPack(BaseImage):
diff --git a/repo2docker/buildpacks/python/__init__.py b/repo2docker/buildpacks/python/__init__.py
index bdcaa520..7aa22564 100644
--- a/repo2docker/buildpacks/python/__init__.py
+++ b/repo2docker/buildpacks/python/__init__.py
@@ -1,8 +1,8 @@
 """Generates Dockerfiles based on an input matrix based on Python."""
 import os
 
-from ..conda import CondaBuildPack
 from ...utils import is_local_pip_requirement, open_guess_encoding
+from ..conda import CondaBuildPack
 
 
 class PythonBuildPack(CondaBuildPack):
diff --git a/repo2docker/buildpacks/r.py b/repo2docker/buildpacks/r.py
index 3156913f..200f472f 100644
--- a/repo2docker/buildpacks/r.py
+++ b/repo2docker/buildpacks/r.py
@@ -1,12 +1,12 @@
-import re
-import os
 import datetime
+import os
+import re
+
 import requests
 
-
 from ..semver import parse_version as V
-from .python import PythonBuildPack
 from ._r_base import rstudio_base_scripts
+from .python import PythonBuildPack
 
 
 class RBuildPack(PythonBuildPack):
diff --git a/repo2docker/contentproviders/__init__.py b/repo2docker/contentproviders/__init__.py
index 6398c233..5c40476d 100755
--- a/repo2docker/contentproviders/__init__.py
+++ b/repo2docker/contentproviders/__init__.py
@@ -1,8 +1,8 @@
-from .git import Git
 from .base import Local
-from .zenodo import Zenodo
-from .figshare import Figshare
 from .dataverse import Dataverse
+from .figshare import Figshare
+from .git import Git
 from .hydroshare import Hydroshare
 from .mercurial import Mercurial
 from .swhid import Swhid
+from .zenodo import Zenodo
diff --git a/repo2docker/contentproviders/dataverse.py b/repo2docker/contentproviders/dataverse.py
index e6e7da38..1998f6be 100644
--- a/repo2docker/contentproviders/dataverse.py
+++ b/repo2docker/contentproviders/dataverse.py
@@ -1,11 +1,10 @@
-import os
 import json
+import os
 import shutil
+from urllib.parse import parse_qs, urlparse, urlunparse
 
-from urllib.parse import urlparse, urlunparse, parse_qs
-
-from .doi import DoiProvider
 from ..utils import copytree, deep_get
+from .doi import DoiProvider
 
 
 class Dataverse(DoiProvider):
diff --git a/repo2docker/contentproviders/doi.py b/repo2docker/contentproviders/doi.py
index 01d048ec..03fa0171 100644
--- a/repo2docker/contentproviders/doi.py
+++ b/repo2docker/contentproviders/doi.py
@@ -1,18 +1,15 @@
-import os
 import json
-import shutil
 import logging
-
-from os import makedirs
-from os import path
-from requests import Session, HTTPError
-
+import os
+import shutil
+from os import makedirs, path
 from zipfile import ZipFile, is_zipfile
 
-from .base import ContentProvider
-from ..utils import copytree, deep_get
-from ..utils import normalize_doi, is_doi
+from requests import HTTPError, Session
+
 from .. import __version__
+from ..utils import copytree, deep_get, is_doi, normalize_doi
+from .base import ContentProvider
 
 
 class DoiProvider(ContentProvider):
diff --git a/repo2docker/contentproviders/figshare.py b/repo2docker/contentproviders/figshare.py
index 0735e441..6c7b26c8 100644
--- a/repo2docker/contentproviders/figshare.py
+++ b/repo2docker/contentproviders/figshare.py
@@ -1,16 +1,14 @@
+import json
 import os
 import re
-import json
 import shutil
-
-from os import makedirs
-from os import path
-from urllib.request import Request
+from os import makedirs, path
 from urllib.error import HTTPError
+from urllib.request import Request
 from zipfile import is_zipfile
 
-from .doi import DoiProvider
 from ..utils import copytree, deep_get
+from .doi import DoiProvider
 
 
 class Figshare(DoiProvider):
diff --git a/repo2docker/contentproviders/git.py b/repo2docker/contentproviders/git.py
index a3d330e6..f35e9a88 100644
--- a/repo2docker/contentproviders/git.py
+++ b/repo2docker/contentproviders/git.py
@@ -1,7 +1,7 @@
 import subprocess
 
+from ..utils import R2dState, check_ref, execute_cmd
 from .base import ContentProvider, ContentProviderException
-from ..utils import execute_cmd, check_ref, R2dState
 
 
 class Git(ContentProvider):
diff --git a/repo2docker/contentproviders/hydroshare.py b/repo2docker/contentproviders/hydroshare.py
index 886a8f81..4104d97a 100755
--- a/repo2docker/contentproviders/hydroshare.py
+++ b/repo2docker/contentproviders/hydroshare.py
@@ -1,14 +1,13 @@
-import zipfile
+import json
 import os
 import shutil
 import time
-import json
-from datetime import datetime, timezone, timedelta
-
+import zipfile
+from datetime import datetime, timedelta, timezone
 from urllib.request import urlretrieve
 
-from .doi import DoiProvider
 from .base import ContentProviderException
+from .doi import DoiProvider
 
 
 class Hydroshare(DoiProvider):
diff --git a/repo2docker/contentproviders/mercurial.py b/repo2docker/contentproviders/mercurial.py
index 821f55f3..e427cc02 100644
--- a/repo2docker/contentproviders/mercurial.py
+++ b/repo2docker/contentproviders/mercurial.py
@@ -1,7 +1,7 @@
 import subprocess
 
+from ..utils import R2dState, execute_cmd
 from .base import ContentProvider, ContentProviderException
-from ..utils import execute_cmd, R2dState
 
 args_enabling_topic = ["--config", "extensions.topic="]
 
diff --git a/repo2docker/contentproviders/swhid.py b/repo2docker/contentproviders/swhid.py
index 2a964e70..18dc78a9 100644
--- a/repo2docker/contentproviders/swhid.py
+++ b/repo2docker/contentproviders/swhid.py
@@ -1,17 +1,16 @@
 import io
 import os
+import re
 import shutil
 import tarfile
 import time
-import re
-
 from os import path
 
 import requests
 
-from .base import ContentProvider
-from ..utils import copytree
 from .. import __version__
+from ..utils import copytree
+from .base import ContentProvider
 
 
 def parse_swhid(swhid):
diff --git a/repo2docker/contentproviders/zenodo.py b/repo2docker/contentproviders/zenodo.py
index 0a8d9108..5d02f723 100644
--- a/repo2docker/contentproviders/zenodo.py
+++ b/repo2docker/contentproviders/zenodo.py
@@ -1,14 +1,12 @@
-import os
 import json
+import os
 import shutil
-
-from os import makedirs
-from os import path
-from urllib.request import Request
+from os import makedirs, path
 from urllib.error import HTTPError
+from urllib.request import Request
 
-from .doi import DoiProvider
 from ..utils import copytree, deep_get
+from .doi import DoiProvider
 
 
 class Zenodo(DoiProvider):
diff --git a/repo2docker/docker.py b/repo2docker/docker.py
index 686a70db..267c16cf 100644
--- a/repo2docker/docker.py
+++ b/repo2docker/docker.py
@@ -2,9 +2,10 @@
 Docker container engine for repo2docker
 """
 
-import docker
-from traitlets import Dict
 from iso8601 import parse_date
+from traitlets import Dict
+
+import docker
 
 from .engine import Container, ContainerEngine, ContainerEngineException, Image
 
diff --git a/repo2docker/engine.py b/repo2docker/engine.py
index 459b2be8..73276a3a 100644
--- a/repo2docker/engine.py
+++ b/repo2docker/engine.py
@@ -3,8 +3,8 @@ Interface for a repo2docker container engine
 """
 
 from abc import ABC, abstractmethod
-from traitlets.config import LoggingConfigurable
 
+from traitlets.config import LoggingConfigurable
 
 # Based on https://docker-py.readthedocs.io/en/4.2.0/containers.html
 
diff --git a/repo2docker/utils.py b/repo2docker/utils.py
index 852f21e2..cd345f4a 100644
--- a/repo2docker/utils.py
+++ b/repo2docker/utils.py
@@ -1,13 +1,12 @@
-from contextlib import contextmanager
-from enum import Enum
-from functools import partial
 import os
 import re
 import subprocess
+from contextlib import contextmanager
+from enum import Enum
+from functools import partial
+from shutil import copy2, copystat
+
 import chardet
-
-from shutil import copystat, copy2
-
 from traitlets import Integer, TraitError
 
 
diff --git a/setup.py b/setup.py
index e4eb16a0..58abff7c 100644
--- a/setup.py
+++ b/setup.py
@@ -1,6 +1,8 @@
-from distutils.cmd import Command
-from setuptools import setup, find_packages
 import sys
+from distutils.cmd import Command
+
+from setuptools import find_packages, setup
+
 import versioneer
 
 if sys.version_info[0] < 3:
@@ -23,8 +25,8 @@ class GenerateDataverseInstallationsFileCommand(Command):
         pass
 
     def run(self):
-        from urllib.request import urlopen
         import json
+        from urllib.request import urlopen
 
         resp = urlopen(self.url, timeout=5)
         resp_body = resp.read()
diff --git a/tests/conda/r3.6-target-repo-dir-flag/verify.py b/tests/conda/r3.6-target-repo-dir-flag/verify.py
index d284c28a..70127836 100755
--- a/tests/conda/r3.6-target-repo-dir-flag/verify.py
+++ b/tests/conda/r3.6-target-repo-dir-flag/verify.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
-import sys
 import os
+import sys
 from glob import glob
 
 # conda should still be in /srv/conda
diff --git a/tests/conftest.py b/tests/conftest.py
index e2914801..13e62b40 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -19,14 +19,13 @@ Test lifecycle:
 import os
 import pipes
 import shlex
-import requests
 import subprocess
 import time
 from tempfile import TemporaryDirectory
 
-
 import escapism
 import pytest
+import requests
 import yaml
 
 from repo2docker.__main__ import make_r2d
diff --git a/tests/memlimit/dockerfile/postBuild b/tests/memlimit/dockerfile/postBuild
index 4fe5360f..1d781924 100755
--- a/tests/memlimit/dockerfile/postBuild
+++ b/tests/memlimit/dockerfile/postBuild
@@ -10,8 +10,8 @@ NOTE: This file has to be duplicated & present in all the following locations:
  - tests/memlimit/dockerfile/postBuild
 See https://github.com/jupyterhub/repo2docker/issues/160 for reason
 """
-from ctypes import cdll, c_void_p, memset
 import os
+from ctypes import c_void_p, cdll, memset
 
 libc = cdll.LoadLibrary("libc.so.6")
 libc.malloc.restype = c_void_p
diff --git a/tests/memlimit/non-dockerfile/postBuild b/tests/memlimit/non-dockerfile/postBuild
index 4fe5360f..1d781924 100755
--- a/tests/memlimit/non-dockerfile/postBuild
+++ b/tests/memlimit/non-dockerfile/postBuild
@@ -10,8 +10,8 @@ NOTE: This file has to be duplicated & present in all the following locations:
  - tests/memlimit/dockerfile/postBuild
 See https://github.com/jupyterhub/repo2docker/issues/160 for reason
 """
-from ctypes import cdll, c_void_p, memset
 import os
+from ctypes import c_void_p, cdll, memset
 
 libc = cdll.LoadLibrary("libc.so.6")
 libc.malloc.restype = c_void_p
diff --git a/tests/pipfile/py2-with-server-and-kernel-req/verify b/tests/pipfile/py2-with-server-and-kernel-req/verify
index 7246be61..5ff8a889 100755
--- a/tests/pipfile/py2-with-server-and-kernel-req/verify
+++ b/tests/pipfile/py2-with-server-and-kernel-req/verify
@@ -2,7 +2,6 @@
 import os
 import sys
 
-
 # Verify - kernel's Python: use Python 2
 print(sys.version_info)
 assert sys.version_info[:2] == (2, 7)
diff --git a/tests/pipfile/setup-py-explicit-in-binder-dir/setup.py b/tests/pipfile/setup-py-explicit-in-binder-dir/setup.py
index c67a722a..ca077f41 100644
--- a/tests/pipfile/setup-py-explicit-in-binder-dir/setup.py
+++ b/tests/pipfile/setup-py-explicit-in-binder-dir/setup.py
@@ -1,4 +1,4 @@
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="Dummy",
diff --git a/tests/pipfile/setup-py-explicit-in-binder-dir/verify b/tests/pipfile/setup-py-explicit-in-binder-dir/verify
index 4c6eaf1e..80f73003 100755
--- a/tests/pipfile/setup-py-explicit-in-binder-dir/verify
+++ b/tests/pipfile/setup-py-explicit-in-binder-dir/verify
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
-import there
 import dummy
 
 # This package should be available, as it was a dependency for dummy
 import pypi_pkg_test
+import there
diff --git a/tests/pipfile/setup-py-explicit/setup.py b/tests/pipfile/setup-py-explicit/setup.py
index c67a722a..ca077f41 100644
--- a/tests/pipfile/setup-py-explicit/setup.py
+++ b/tests/pipfile/setup-py-explicit/setup.py
@@ -1,4 +1,4 @@
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="Dummy",
diff --git a/tests/pipfile/setup-py-explicit/verify b/tests/pipfile/setup-py-explicit/verify
index 4c6eaf1e..80f73003 100755
--- a/tests/pipfile/setup-py-explicit/verify
+++ b/tests/pipfile/setup-py-explicit/verify
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
-import there
 import dummy
 
 # This package should be available, as it was a dependency for dummy
 import pypi_pkg_test
+import there
diff --git a/tests/pipfile/setup-py-implicit/setup.py b/tests/pipfile/setup-py-implicit/setup.py
index c67a722a..ca077f41 100644
--- a/tests/pipfile/setup-py-implicit/setup.py
+++ b/tests/pipfile/setup-py-implicit/setup.py
@@ -1,4 +1,4 @@
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="Dummy",
diff --git a/tests/unit/contentproviders/test_dataverse.py b/tests/unit/contentproviders/test_dataverse.py
index 63a58471..309a22d4 100644
--- a/tests/unit/contentproviders/test_dataverse.py
+++ b/tests/unit/contentproviders/test_dataverse.py
@@ -1,16 +1,15 @@
 import json
 import os
-import pytest
 import re
-
 from io import BytesIO
 from tempfile import TemporaryDirectory
 from unittest.mock import patch
-from urllib.request import urlopen, Request
+from urllib.request import Request, urlopen
+
+import pytest
 
 from repo2docker.contentproviders import Dataverse
 
-
 test_dv = Dataverse()
 harvard_dv = next(_ for _ in test_dv.hosts if _["name"] == "Harvard Dataverse")
 cimmyt_dv = next(_ for _ in test_dv.hosts if _["name"] == "CIMMYT Research Data")
diff --git a/tests/unit/contentproviders/test_doi.py b/tests/unit/contentproviders/test_doi.py
index ed2dcb73..dab3d7fc 100644
--- a/tests/unit/contentproviders/test_doi.py
+++ b/tests/unit/contentproviders/test_doi.py
@@ -1,17 +1,17 @@
 import json
+import logging
 import os
 import re
-import urllib
-import pytest
 import tempfile
-import logging
-
-from unittest.mock import patch, MagicMock, mock_open
+import urllib
+from unittest.mock import MagicMock, mock_open, patch
 from zipfile import ZipFile
 
-from repo2docker.contentproviders.doi import DoiProvider
-from repo2docker.contentproviders.base import ContentProviderException
+import pytest
+
 from repo2docker import __version__
+from repo2docker.contentproviders.base import ContentProviderException
+from repo2docker.contentproviders.doi import DoiProvider
 
 
 def test_content_id():
diff --git a/tests/unit/contentproviders/test_figshare.py b/tests/unit/contentproviders/test_figshare.py
index 3de67e98..b4f42de3 100644
--- a/tests/unit/contentproviders/test_figshare.py
+++ b/tests/unit/contentproviders/test_figshare.py
@@ -1,18 +1,17 @@
 import json
 import os
 import re
-import pytest
-
 from contextlib import contextmanager
 from io import BytesIO
-from tempfile import TemporaryDirectory, NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 from unittest.mock import patch
-from urllib.request import urlopen, Request
+from urllib.request import Request, urlopen
 from zipfile import ZipFile
 
-from repo2docker.contentproviders import Figshare
-from repo2docker.__main__ import make_r2d
+import pytest
 
+from repo2docker.__main__ import make_r2d
+from repo2docker.contentproviders import Figshare
 
 test_content_ids = [
     ("https://figshare.com/articles/title/9782777", "9782777.v1"),
diff --git a/tests/unit/contentproviders/test_git.py b/tests/unit/contentproviders/test_git.py
index 65779bf6..fd63f968 100644
--- a/tests/unit/contentproviders/test_git.py
+++ b/tests/unit/contentproviders/test_git.py
@@ -1,7 +1,9 @@
 import os
-import pytest
 import subprocess
 from tempfile import TemporaryDirectory
+
+import pytest
+
 from repo2docker.contentproviders import Git
 
 
diff --git a/tests/unit/contentproviders/test_hydroshare.py b/tests/unit/contentproviders/test_hydroshare.py
index b0211c52..cec541f6 100755
--- a/tests/unit/contentproviders/test_hydroshare.py
+++ b/tests/unit/contentproviders/test_hydroshare.py
@@ -1,16 +1,15 @@
 import os
-import pytest
-
+import re
 from contextlib import contextmanager
-from tempfile import TemporaryDirectory, NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 from unittest.mock import patch
 from zipfile import ZipFile
-import re
+
+import pytest
 
 from repo2docker.contentproviders import Hydroshare
 from repo2docker.contentproviders.base import ContentProviderException
 
-
 doi_responses = {
     "https://doi.org/10.4211/hs.b8f6eae9d89241cf8b5904033460af61": (
         "https://www.hydroshare.org/resource/b8f6eae9d89241cf8b5904033460af61"
diff --git a/tests/unit/contentproviders/test_local.py b/tests/unit/contentproviders/test_local.py
index fcb2a6a8..ef288aef 100644
--- a/tests/unit/contentproviders/test_local.py
+++ b/tests/unit/contentproviders/test_local.py
@@ -1,5 +1,5 @@
 import os
-from tempfile import TemporaryDirectory, NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 
 from repo2docker.contentproviders import Local
 
diff --git a/tests/unit/contentproviders/test_mercurial.py b/tests/unit/contentproviders/test_mercurial.py
index 4619ef86..0acb91d1 100644
--- a/tests/unit/contentproviders/test_mercurial.py
+++ b/tests/unit/contentproviders/test_mercurial.py
@@ -8,7 +8,6 @@ import pytest
 from repo2docker.contentproviders import Mercurial
 from repo2docker.contentproviders.mercurial import args_enabling_topic
 
-
 SKIP_HG = os.environ.get("REPO2DOCKER_SKIP_HG_TESTS", "").lower() not in {
     "",
     "0",
diff --git a/tests/unit/contentproviders/test_swhid.py b/tests/unit/contentproviders/test_swhid.py
index 48c1fa31..56fee1df 100644
--- a/tests/unit/contentproviders/test_swhid.py
+++ b/tests/unit/contentproviders/test_swhid.py
@@ -1,22 +1,22 @@
-import json
-import os
 import io
-import tarfile
-import shutil
-import re
-import urllib
-import pytest
-import tempfile
+import json
 import logging
-import requests_mock
-
+import os
+import re
+import shutil
+import tarfile
+import tempfile
+import urllib
 from os import makedirs
 from os.path import join
-from unittest.mock import patch, MagicMock, mock_open
+from unittest.mock import MagicMock, mock_open, patch
 from zipfile import ZipFile
 
-from repo2docker.contentproviders.swhid import Swhid, parse_swhid
+import pytest
+import requests_mock
+
 from repo2docker.contentproviders.base import ContentProviderException
+from repo2docker.contentproviders.swhid import Swhid, parse_swhid
 
 
 # this is a slightly stripped down copy of swh.model.cli.swhid_of_dir().
diff --git a/tests/unit/contentproviders/test_zenodo.py b/tests/unit/contentproviders/test_zenodo.py
index 88e143c6..0755163d 100644
--- a/tests/unit/contentproviders/test_zenodo.py
+++ b/tests/unit/contentproviders/test_zenodo.py
@@ -1,15 +1,15 @@
 import json
 import os
-import pytest
 import re
-
 from contextlib import contextmanager
 from io import BytesIO
-from tempfile import TemporaryDirectory, NamedTemporaryFile
+from tempfile import NamedTemporaryFile, TemporaryDirectory
 from unittest.mock import patch
-from urllib.request import urlopen, Request
+from urllib.request import Request, urlopen
 from zipfile import ZipFile
 
+import pytest
+
 from repo2docker.contentproviders import Zenodo
 
 doi_responses = {
diff --git a/tests/unit/test_app.py b/tests/unit/test_app.py
index 25b39cdb..d37103e6 100644
--- a/tests/unit/test_app.py
+++ b/tests/unit/test_app.py
@@ -1,13 +1,13 @@
 import errno
-import pytest
 from tempfile import TemporaryDirectory
 from unittest.mock import patch
 
-import docker
 import escapism
+import pytest
 
-from repo2docker.app import Repo2Docker
+import docker
 from repo2docker.__main__ import make_r2d
+from repo2docker.app import Repo2Docker
 from repo2docker.utils import chdir
 
 
diff --git a/tests/unit/test_args.py b/tests/unit/test_args.py
index 404ee796..975604ea 100644
--- a/tests/unit/test_args.py
+++ b/tests/unit/test_args.py
@@ -2,9 +2,11 @@
 Test argument parsing and r2d construction
 """
 import os
+
 import pytest
-from repo2docker.__main__ import make_r2d
+
 from repo2docker import __version__
+from repo2docker.__main__ import make_r2d
 
 
 def test_version(capsys):
diff --git a/tests/unit/test_argumentvalidation.py b/tests/unit/test_argumentvalidation.py
index d2475b89..33e7d69a 100644
--- a/tests/unit/test_argumentvalidation.py
+++ b/tests/unit/test_argumentvalidation.py
@@ -7,7 +7,6 @@ import subprocess
 
 import pytest
 
-
 here = os.path.dirname(os.path.abspath(__file__))
 test_dir = os.path.dirname(here)
 docker_simple = os.path.join(test_dir, "dockerfile", "simple")
diff --git a/tests/unit/test_buildpack.py b/tests/unit/test_buildpack.py
index eda7bb92..6a8147e3 100644
--- a/tests/unit/test_buildpack.py
+++ b/tests/unit/test_buildpack.py
@@ -1,7 +1,8 @@
 from os.path import join as pjoin
+from tempfile import TemporaryDirectory
 
 import pytest
-from tempfile import TemporaryDirectory
+
 from repo2docker.buildpacks import LegacyBinderDockerBuildPack, PythonBuildPack
 from repo2docker.utils import chdir
 
diff --git a/tests/unit/test_cache_from.py b/tests/unit/test_cache_from.py
index 77797b12..fd186dbc 100644
--- a/tests/unit/test_cache_from.py
+++ b/tests/unit/test_cache_from.py
@@ -5,7 +5,6 @@ Test that --cache-from is passed in to docker API properly.
 from unittest.mock import MagicMock
 
 import docker
-
 from repo2docker.buildpacks import (
     BaseImage,
     DockerBuildPack,
diff --git a/tests/unit/test_clone_depth.py b/tests/unit/test_clone_depth.py
index 7989b117..55102eac 100644
--- a/tests/unit/test_clone_depth.py
+++ b/tests/unit/test_clone_depth.py
@@ -8,12 +8,10 @@ and that is the only thing that is tested.
 """
 import os
 import subprocess
-
 from tempfile import TemporaryDirectory
 
 from repo2docker.app import Repo2Docker
 
-
 URL = "https://github.com/binderhub-ci-repos/repo2docker-ci-clone-depth"
 
 
diff --git a/tests/unit/test_connect_url.py b/tests/unit/test_connect_url.py
index 7438b8aa..dbc0c260 100644
--- a/tests/unit/test_connect_url.py
+++ b/tests/unit/test_connect_url.py
@@ -1,10 +1,11 @@
 """
 Test if the explict hostname is supplied correctly to the container
 """
-import requests
 import time
-from repo2docker.app import Repo2Docker
 
+import requests
+
+from repo2docker.app import Repo2Docker
 
 # Minimal Dockerfile to make build as fast as possible
 DOCKER_FILE = """
diff --git a/tests/unit/test_editable.py b/tests/unit/test_editable.py
index 6947b7d2..de4d6261 100644
--- a/tests/unit/test_editable.py
+++ b/tests/unit/test_editable.py
@@ -5,7 +5,6 @@ import time
 
 from repo2docker.__main__ import make_r2d
 
-
 DIR = os.path.join(os.path.dirname(os.path.dirname(__file__)), "dockerfile", "editable")
 
 
diff --git a/tests/unit/test_env_yml.py b/tests/unit/test_env_yml.py
index c744ccf3..dff14228 100644
--- a/tests/unit/test_env_yml.py
+++ b/tests/unit/test_env_yml.py
@@ -3,7 +3,9 @@ Test if the environment.yml is empty or it constains other data structure than a
 """
 import os
 import sys
+
 import pytest
+
 from repo2docker import buildpacks
 
 
diff --git a/tests/unit/test_external_scripts.py b/tests/unit/test_external_scripts.py
index d03debe5..278707c8 100644
--- a/tests/unit/test_external_scripts.py
+++ b/tests/unit/test_external_scripts.py
@@ -1,5 +1,6 @@
 """Test if assemble scripts from outside of r2d repo are accepted."""
 import time
+
 from repo2docker.app import Repo2Docker
 from repo2docker.buildpacks import PythonBuildPack
 
diff --git a/tests/unit/test_freeze.py b/tests/unit/test_freeze.py
index 66b0c3bb..ddcd29f3 100644
--- a/tests/unit/test_freeze.py
+++ b/tests/unit/test_freeze.py
@@ -2,12 +2,11 @@ import os
 from tempfile import TemporaryDirectory
 from unittest.mock import patch
 
+import pytest
 from ruamel.yaml import YAML
 
 from repo2docker.buildpacks.conda.freeze import set_python
 
-import pytest
-
 V = "3.7"
 yaml = YAML(typ="rt")
 
diff --git a/tests/unit/test_labels.py b/tests/unit/test_labels.py
index c13cff4b..5520de4d 100644
--- a/tests/unit/test_labels.py
+++ b/tests/unit/test_labels.py
@@ -1,12 +1,13 @@
 """
 Test if labels are supplied correctly to the container
 """
-from repo2docker.app import Repo2Docker
-from repo2docker.buildpacks import BuildPack
-from repo2docker import __version__
-import pytest
 from unittest.mock import Mock
 
+import pytest
+
+from repo2docker import __version__
+from repo2docker.app import Repo2Docker
+from repo2docker.buildpacks import BuildPack
 
 URL = "https://github.com/binderhub-ci-repos/repo2docker-ci-clone-depth"
 
diff --git a/tests/unit/test_memlimit.py b/tests/unit/test_memlimit.py
index 1e708d4f..ee2f2b35 100644
--- a/tests/unit/test_memlimit.py
+++ b/tests/unit/test_memlimit.py
@@ -3,16 +3,13 @@ Test that build time memory limits are enforced
 """
 
 import os
-
 from unittest.mock import MagicMock
 
-import docker
-
 import pytest
 
+import docker
 from repo2docker.buildpacks import BaseImage, DockerBuildPack
 
-
 basedir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 
diff --git a/tests/unit/test_ports.py b/tests/unit/test_ports.py
index 90148ba4..aaebcdab 100644
--- a/tests/unit/test_ports.py
+++ b/tests/unit/test_ports.py
@@ -2,18 +2,18 @@
 Test Port mappings work on running non-jupyter workflows
 """
 
-import requests
-import time
 import os
-import tempfile
 import random
+import tempfile
+import time
 from getpass import getuser
 
-import docker
 import pytest
+import requests
 
-from repo2docker.app import Repo2Docker
+import docker
 from repo2docker.__main__ import make_r2d
+from repo2docker.app import Repo2Docker
 
 
 def read_port_mapping_response(
diff --git a/tests/unit/test_r.py b/tests/unit/test_r.py
index 3d141cfc..a5d7db7c 100644
--- a/tests/unit/test_r.py
+++ b/tests/unit/test_r.py
@@ -1,8 +1,8 @@
 from datetime import date
+from unittest.mock import patch
 
 import pytest
 from requests.models import Response
-from unittest.mock import patch
 
 from repo2docker import buildpacks
 
diff --git a/tests/unit/test_semver.py b/tests/unit/test_semver.py
index bbbf8ca5..b07272be 100644
--- a/tests/unit/test_semver.py
+++ b/tests/unit/test_semver.py
@@ -1,5 +1,6 @@
 import pytest
 from semver import VersionInfo
+
 from repo2docker import semver
 
 
diff --git a/tests/unit/test_subdir.py b/tests/unit/test_subdir.py
index 4b0cd47b..4e700731 100644
--- a/tests/unit/test_subdir.py
+++ b/tests/unit/test_subdir.py
@@ -4,8 +4,8 @@ Test if the subdirectory is correctly navigated to
 import os
 
 import escapism
-
 import pytest
+
 from repo2docker.app import Repo2Docker
 
 TEST_REPO = "https://github.com/binderhub-ci-repos/repo2docker-subdir-support"
diff --git a/tests/unit/test_utils.py b/tests/unit/test_utils.py
index 28401e33..cec3dc8c 100644
--- a/tests/unit/test_utils.py
+++ b/tests/unit/test_utils.py
@@ -1,13 +1,15 @@
 """
 Tests for repo2docker/utils.py
 """
-import traitlets
 import os
-from repo2docker import utils
-import pytest
 import subprocess
 import tempfile
 
+import pytest
+import traitlets
+
+from repo2docker import utils
+
 
 def test_capture_cmd_no_capture_success():
     # This should succeed