opt-out of auto-freezing Python 3.5

now that it's not being updated anymore

only security fixes from now on for Python 3.5

repo2docker/buildpacks/conda/environment.py-3.5.frozen.yml

@@ -1,5 +1,6 @@
-# AUTO GENERATED FROM environment.py-3.5.yml, DO NOT MANUALLY MODIFY
-# Frozen on 2018-11-20 06:16:12 UTC
+# py3.5 conda packages are no longer being updated as of 12/2018
+# this file is hand-maintained now
+# and should only receive security fixes, no new features
 name: r2d
 channels:
   - conda-forge
@@ -75,6 +76,7 @@ dependencies:
     - idna==2.7
     - jupyterhub==0.9.4
     - mako==1.0.7
+    - notebook==5.7.2
     - nteract-on-jupyter==1.9.6
     - pamela==0.3.0
     - python-editor==1.0.3

repo2docker/buildpacks/conda/environment.py-3.5.yml

@@ -1,3 +1,5 @@
+# py3.5 is not being auto-generated from this file anymore
+# update environment.py-3.5.frozen.yml directly
 dependencies:
 - python=3.5.*
 - ipywidgets==7.2.1

repo2docker/buildpacks/conda/freeze.py

@@ -45,9 +45,16 @@ def freeze(env_file, frozen_file):
 
     Result will be stored in frozen_file
     """
+    frozen_dest = HERE / frozen_file
+    if frozen_dest.exists():
+        with frozen_dest.open('r') as f:
+            line = f.readline()
+            if 'GENERATED' not in line:
+                print(f"{frozen_file} not autogenerated, not refreezing")
+                return
     print(f"Freezing {env_file} -> {frozen_file}")
 
-    with open(HERE / frozen_file, 'w') as f:
+    with frozen_dest.open('w') as f:
         f.write(f"# AUTO GENERATED FROM {env_file}, DO NOT MANUALLY MODIFY\n")
         f.write(f"# Frozen on {datetime.utcnow():%Y-%m-%d %H:%M:%S UTC}\n")
 
@@ -78,8 +85,8 @@ def set_python(py_env_file, py):
     if os.path.exists(py_env_file):
         # only clobber auto-generated files
         with open(py_env_file) as f:
-            text = f.read()
-            if text and 'GENERATED' not in text:
+            text = f.readline()
+            if 'GENERATED' not in text:
                 return
 
     print(f"Regenerating {py_env_file} from {ENV_FILE}")