prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Current `tox` configuration ends up testing old code
  For example:
  
  ``` bash
  $ rm -r .tox/
  $ tox -e system-tests --notest
  GLOB sdist-make: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/setup.py
  system-tests create: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/.tox/system-tests
  system-tests inst: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/.tox/dist/google-cloud-0.20.0.zip
  system-tests installed: -f file:///home/tseaver/.pip/wheels,enum34==1.1.6,future==0.15.2,futures==3.0.5,gapic-google-logging-v2==0.10.1,gapic-google-pubsub-v1==0.10.1,google-cloud==0.20.0,google-cloud-bigquery==0.20.0,google-cloud-bigtable==0.20.0,google-cloud-core==0.20.0,google-cloud-datastore==0.20.0,google-cloud-dns==0.20.0,google-cloud-error-reporting==0.20.0,google-cloud-happybase==0.20.0,google-cloud-language==0.20.0,google-cloud-logging==0.20.0,google-cloud-monitoring==0.20.0,google-cloud-pubsub==0.20.0,google-cloud-resource-manager==0.20.0,google-cloud-storage==0.20.0,google-cloud-translate==0.20.0,google-cloud-vision==0.20.0,google-gax==0.14.1,googleapis-common-protos==1.3.5,grpc-google-iam-v1==0.10.1,grpc-google-logging-v2==0.10.1,grpc-google-pubsub-v1==0.10.1,grpcio==1.0.0,httplib2==0.9.2,oauth2client==3.0.0,ply==3.8,protobuf==3.1.0.post1,pyasn1==0.1.9,pyasn1-modules==0.0.8,rsa==3.4.2,six==1.10.0
  ___________________________________ summary ____________________________________
    system-tests: skipped tests
    congratulations :)
  $ diff -ru .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/ storage/google/cloud/storage/ --exclude="*.pyc"
  diff -ru '--exclude=*.pyc' .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/blob.py storage/google/cloud/storage/blob.py
  --- .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/blob.py  2016-10-05 18:15:48.724796000 -0400
  +++ storage/google/cloud/storage/blob.py    2016-10-05 18:02:55.872830411 -0400
  @@ -655,6 +655,32 @@
           self.acl.all().grant_read()
           self.acl.save(client=client)
  
  +    def compose(self, sources, client=None):
  +        """Concatenate source blobs into this one.
  +
  +        :type sources: list of :class:`Blob`
  +        :param sources: blobs whose contents will be composed into this blob.
  +
  +        :type client: :class:`~google.cloud.storage.client.Client` or
  +                      ``NoneType``
  +        :param client: Optional. The client to use.  If not passed, falls back
  +                       to the ``client`` stored on the blob's bucket.
  +
  +        :raises: :exc:`ValueError` if this blob does not have its
  +                 :attr:`content_type` set.
  +        """
  +        if self.content_type is None:
  +            raise ValueError("Destination 'content_type' not set.")
  +        client = self._require_client(client)
  +        request = {
  +            'sourceObjects': [{'name': source.name} for source in sources],
  +            'destination': self._properties.copy(),
  +        }
  +        api_response = client.connection.api_request(
  +            method='POST', path=self.path + '/compose', data=request,
  +            _target_object=self)
  +        self._set_properties(api_response)
  +
       cache_control = _scalar_property('cacheControl')
       """HTTP 'Cache-Control' header for this object.
  ```
  
  Somehow, the tarball / wheel is being cached.
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `scripts/pycodestyle_on_repo.py`
  Content:
  ```
  1 # Copyright 2016 Google Inc.
  2 #
  3 # Licensed under the Apache License, Version 2.0 (the "License");
  4 # you may not use this file except in compliance with the License.
  5 # You may obtain a copy of the License at
  6 #
  7 #     http://www.apache.org/licenses/LICENSE-2.0
  8 #
  9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS,
  11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 # See the License for the specific language governing permissions and
  13 # limitations under the License.
  14 
  15 """Custom script to run pycodestyle on google-cloud codebase.
  16 
  17 This runs pycodestyle as a script via subprocess but only runs it on the
  18 .py files that are checked in to the repository.
  19 """
  20 
  21 
  22 import os
  23 import subprocess
  24 import sys
  25 
  26 from script_utils import get_affected_files
  27 
  28 
  29 def main():
  30     """Run pycodestyle on all Python files in the repository."""
  31     git_root = subprocess.check_output(
  32         ['git', 'rev-parse', '--show-toplevel']).strip()
  33     os.chdir(git_root)
  34     candidates, _ = get_affected_files()
  35     python_files = [
  36         candidate for candidate in candidates if candidate.endswith('.py')]
  37 
  38     pycodestyle_command = ['pycodestyle'] + python_files
  39     status_code = subprocess.call(pycodestyle_command)
  40     sys.exit(status_code)
  41 
  42 
  43 if __name__ == '__main__':
  44     main()
  45
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/scripts/pycodestyle_on_repo.py b/scripts/pycodestyle_on_repo.py
  --- a/scripts/pycodestyle_on_repo.py
  +++ b/scripts/pycodestyle_on_repo.py
  @@ -19,6 +19,8 @@
   """
   
   
  +from __future__ import print_function
  +
   import os
   import subprocess
   import sys
  @@ -35,9 +37,12 @@
       python_files = [
           candidate for candidate in candidates if candidate.endswith('.py')]
   
  -    pycodestyle_command = ['pycodestyle'] + python_files
  -    status_code = subprocess.call(pycodestyle_command)
  -    sys.exit(status_code)
  +    if not python_files:
  +        print('No Python files to lint, exiting.')
  +    else:
  +        pycodestyle_command = ['pycodestyle'] + python_files
  +        status_code = subprocess.call(pycodestyle_command)
  +        sys.exit(status_code)
   
   
   if __name__ == '__main__':
  
verification_info: {"golden_diff": "diff --git a/scripts/pycodestyle_on_repo.py b/scripts/pycodestyle_on_repo.py\n--- a/scripts/pycodestyle_on_repo.py\n+++ b/scripts/pycodestyle_on_repo.py\n@@ -19,6 +19,8 @@\n \"\"\"\n \n \n+from __future__ import print_function\n+\n import os\n import subprocess\n import sys\n@@ -35,9 +37,12 @@\n     python_files = [\n         candidate for candidate in candidates if candidate.endswith('.py')]\n \n-    pycodestyle_command = ['pycodestyle'] + python_files\n-    status_code = subprocess.call(pycodestyle_command)\n-    sys.exit(status_code)\n+    if not python_files:\n+        print('No Python files to lint, exiting.')\n+    else:\n+        pycodestyle_command = ['pycodestyle'] + python_files\n+        status_code = subprocess.call(pycodestyle_command)\n+        sys.exit(status_code)\n \n \n if __name__ == '__main__':\n", "issue": "Current `tox` configuration ends up testing old code\nFor example:\n\n``` bash\n$ rm -r .tox/\n$ tox -e system-tests --notest\nGLOB sdist-make: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/setup.py\nsystem-tests create: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/.tox/system-tests\nsystem-tests inst: /home/tseaver/projects/agendaless/Google/src/google-cloud-python/.tox/dist/google-cloud-0.20.0.zip\nsystem-tests installed: -f file:///home/tseaver/.pip/wheels,enum34==1.1.6,future==0.15.2,futures==3.0.5,gapic-google-logging-v2==0.10.1,gapic-google-pubsub-v1==0.10.1,google-cloud==0.20.0,google-cloud-bigquery==0.20.0,google-cloud-bigtable==0.20.0,google-cloud-core==0.20.0,google-cloud-datastore==0.20.0,google-cloud-dns==0.20.0,google-cloud-error-reporting==0.20.0,google-cloud-happybase==0.20.0,google-cloud-language==0.20.0,google-cloud-logging==0.20.0,google-cloud-monitoring==0.20.0,google-cloud-pubsub==0.20.0,google-cloud-resource-manager==0.20.0,google-cloud-storage==0.20.0,google-cloud-translate==0.20.0,google-cloud-vision==0.20.0,google-gax==0.14.1,googleapis-common-protos==1.3.5,grpc-google-iam-v1==0.10.1,grpc-google-logging-v2==0.10.1,grpc-google-pubsub-v1==0.10.1,grpcio==1.0.0,httplib2==0.9.2,oauth2client==3.0.0,ply==3.8,protobuf==3.1.0.post1,pyasn1==0.1.9,pyasn1-modules==0.0.8,rsa==3.4.2,six==1.10.0\n___________________________________ summary ____________________________________\n  system-tests: skipped tests\n  congratulations :)\n$ diff -ru .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/ storage/google/cloud/storage/ --exclude=\"*.pyc\"\ndiff -ru '--exclude=*.pyc' .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/blob.py storage/google/cloud/storage/blob.py\n--- .tox/system-tests/lib/python2.7/site-packages/google/cloud/storage/blob.py  2016-10-05 18:15:48.724796000 -0400\n+++ storage/google/cloud/storage/blob.py    2016-10-05 18:02:55.872830411 -0400\n@@ -655,6 +655,32 @@\n         self.acl.all().grant_read()\n         self.acl.save(client=client)\n\n+    def compose(self, sources, client=None):\n+        \"\"\"Concatenate source blobs into this one.\n+\n+        :type sources: list of :class:`Blob`\n+        :param sources: blobs whose contents will be composed into this blob.\n+\n+        :type client: :class:`~google.cloud.storage.client.Client` or\n+                      ``NoneType``\n+        :param client: Optional. The client to use.  If not passed, falls back\n+                       to the ``client`` stored on the blob's bucket.\n+\n+        :raises: :exc:`ValueError` if this blob does not have its\n+                 :attr:`content_type` set.\n+        \"\"\"\n+        if self.content_type is None:\n+            raise ValueError(\"Destination 'content_type' not set.\")\n+        client = self._require_client(client)\n+        request = {\n+            'sourceObjects': [{'name': source.name} for source in sources],\n+            'destination': self._properties.copy(),\n+        }\n+        api_response = client.connection.api_request(\n+            method='POST', path=self.path + '/compose', data=request,\n+            _target_object=self)\n+        self._set_properties(api_response)\n+\n     cache_control = _scalar_property('cacheControl')\n     \"\"\"HTTP 'Cache-Control' header for this object.\n```\n\nSomehow, the tarball / wheel is being cached.\n\n", "before_files": [{"content": "# Copyright 2016 Google Inc.\n#\n# Licensed under the Apache License, Version 2.0 (the \"License\");\n# you may not use this file except in compliance with the License.\n# You may obtain a copy of the License at\n#\n#     http://www.apache.org/licenses/LICENSE-2.0\n#\n# Unless required by applicable law or agreed to in writing, software\n# distributed under the License is distributed on an \"AS IS\" BASIS,\n# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n# See the License for the specific language governing permissions and\n# limitations under the License.\n\n\"\"\"Custom script to run pycodestyle on google-cloud codebase.\n\nThis runs pycodestyle as a script via subprocess but only runs it on the\n.py files that are checked in to the repository.\n\"\"\"\n\n\nimport os\nimport subprocess\nimport sys\n\nfrom script_utils import get_affected_files\n\n\ndef main():\n    \"\"\"Run pycodestyle on all Python files in the repository.\"\"\"\n    git_root = subprocess.check_output(\n        ['git', 'rev-parse', '--show-toplevel']).strip()\n    os.chdir(git_root)\n    candidates, _ = get_affected_files()\n    python_files = [\n        candidate for candidate in candidates if candidate.endswith('.py')]\n\n    pycodestyle_command = ['pycodestyle'] + python_files\n    status_code = subprocess.call(pycodestyle_command)\n    sys.exit(status_code)\n\n\nif __name__ == '__main__':\n    main()\n", "path": "scripts/pycodestyle_on_repo.py"}], "after_files": [{"content": "# Copyright 2016 Google Inc.\n#\n# Licensed under the Apache License, Version 2.0 (the \"License\");\n# you may not use this file except in compliance with the License.\n# You may obtain a copy of the License at\n#\n#     http://www.apache.org/licenses/LICENSE-2.0\n#\n# Unless required by applicable law or agreed to in writing, software\n# distributed under the License is distributed on an \"AS IS\" BASIS,\n# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n# See the License for the specific language governing permissions and\n# limitations under the License.\n\n\"\"\"Custom script to run pycodestyle on google-cloud codebase.\n\nThis runs pycodestyle as a script via subprocess but only runs it on the\n.py files that are checked in to the repository.\n\"\"\"\n\n\nfrom __future__ import print_function\n\nimport os\nimport subprocess\nimport sys\n\nfrom script_utils import get_affected_files\n\n\ndef main():\n    \"\"\"Run pycodestyle on all Python files in the repository.\"\"\"\n    git_root = subprocess.check_output(\n        ['git', 'rev-parse', '--show-toplevel']).strip()\n    os.chdir(git_root)\n    candidates, _ = get_affected_files()\n    python_files = [\n        candidate for candidate in candidates if candidate.endswith('.py')]\n\n    if not python_files:\n        print('No Python files to lint, exiting.')\n    else:\n        pycodestyle_command = ['pycodestyle'] + python_files\n        status_code = subprocess.call(pycodestyle_command)\n        sys.exit(status_code)\n\n\nif __name__ == '__main__':\n    main()\n", "path": "scripts/pycodestyle_on_repo.py"}]}