Make checkperms.py look for shebang.

tools/checkperms/checkperms.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Makes sure files have the right permissions.
 
 Some developers have broken SCM configurations that flip the svn:executable
 permission on for no good reason. Unix developers who run ls --color will then
 see .cc files in green and get confused.
@@ skipping 159 matching lines @@
 
   # Not whitelisted, stat the file and check permissions.
   try:
     st_mode = os.stat(file_path).st_mode
   except IOError, e:
     return 'Failed to stat file: %s' % e
   except OSError, e:
     return 'Failed to stat file: %s' % e
 
   if EXECUTABLE_PERMISSION & st_mode:
+    # Look if the file starts with #!/
+    with open(file_path, 'rb') as f:
+      if f.read(3) == '#!/':
+        # That's fine.
+        return None
+    # TODO(maruel): Check that non-executable file do not start with a shebang.
     error = 'Contains executable permission'
     if VERBOSE:
       return '%s: %06o' % (error, st_mode)
     return error
   return None
 
 
 def ShouldCheckDirectory(dir_path):
   """Determine if we should check the content of dir_path."""
   if not IS_SVN:
@@ skipping 144 matching lines @@
     success = CheckDirectory(start_dir)
   if not success:
     print '\nFAILED\n'
     return 1
   print '\nSUCCESS\n'
   return 0
 
 
 if '__main__' == __name__:
   sys.exit(main(sys.argv))