[telemetry] Move stale .pyc check from Python import to gclient hook.

DEPS

 # This file is automatically processed to create .DEPS.git which is the file
 # that gclient uses under git.
 #
 # See http://code.google.com/p/chromium/wiki/UsingGit
 #
 # To test manually, run:
 #   python tools/deps2git/deps2git.py -o .DEPS.git -w <gclientdir>
 # where <gcliendir> is the absolute path to the directory containing the
 # .gclient file (the parent of 'src').
 #
@@ skipping 760 matching lines @@
     # write access to the git repo. To be removed sometime after Chrome to git
     # migration completes (let's say Sep 1 2014).
     'name': 'check_git_config',
     'pattern': '.',
     'action': [
         'python',
         'src/tools/check_git_config.py',
         '--running-as-hook',
     ],
   },
+  {
+    # Ensure that we don't accidentally reference any .pyc files whose
+    # corresponding .py files have already been deleted.
+    'name': 'remove_stale_pyc_files',
+    'pattern': 'src/tools/.*\\.py',
+    'action': [
+        'python',
+        'src/tools/remove_stale_pyc_files.py',
+        'src/tools',
+    ],
+  },
 ]