Remove traitlet imports from all buildpacks

repo2docker/buildpacks/base.py

@@ -1,6 +1,5 @@
 import textwrap
 from traitlets.config import LoggingConfigurable
-from traitlets import Unicode, Set, List, Dict, Tuple, default
 import jinja2
 import tarfile
 import io

repo2docker/buildpacks/conda/__init__.py

@@ -6,7 +6,6 @@ import os
 import re
 
 from ruamel.yaml import YAML
-from traitlets import default, Unicode
 
 from ..base import BaseImage
 

repo2docker/buildpacks/julia.py

@@ -1,7 +1,6 @@
 """
 Generates a variety of Dockerfiles based on an input matrix
 """
-from traitlets import default
 import os
 from .conda import CondaBuildPack
 

repo2docker/buildpacks/python/__init__.py

@@ -1,7 +1,6 @@
 """
 Generates a variety of Dockerfiles based on an input matrix
 """
-from traitlets import default
 import os
 from ..base import BaseImage