Using Python script to run pep8 instead of bash.

We require a script (Python or bash) since we only run
pep8 on files that are checked in to the repo by using
`git ls-files`. (Prior to this change, spurious Python files
would cause `tox -e lint` to fail.)

Author: dhermes

scripts/pep8_on_repo.py

@@ -0,0 +1,39 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Custom script to run pep8 on gcloud codebase.
+
+This runs pep8 as a script via subprocess but only runs it on the
+.py files that are checked in to the repository.
+"""
+
+
+import os
+import subprocess
+
+
+def main():
+    """Run pep8 on all Python files in the repository."""
+    git_root = subprocess.check_output(
+        ['git', 'rev-parse', '--show-toplevel']).strip()
+    os.chdir(git_root)
+    python_files = subprocess.check_output(['git', 'ls-files', '*py'])
+    python_files = python_files.strip().split()
+
+    pep8_command = ['pep8'] + python_files
+    subprocess.call(pep8_command)
+
+
+if __name__ == '__main__':
+    main()

scripts/pep8_on_repo.sh

@@ -70,7 +70,7 @@ verbose = 1
 basepython =
     python2.7
 commands =
-    {toxinidir}/scripts/pep8_on_repo.sh
+    python {toxinidir}/scripts/pep8_on_repo.py
     python {toxinidir}/scripts/run_pylint.py
 deps =
     pep8