Suppress pychecker warnings about the python standard library

tools/code_hygiene.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Simple Code Hygiene tool meant to be run as a presubmit test or standalone
 
 Usage:
 ./code_hygiene.py <file1> <file2> ...
 
@@ skipping 40 matching lines @@
              ',-build/include_order'
              ',-readability/casting'
              ',-readability/check'
              ',-readability/multiline_comment'
              ',-runtime/sizeof'
              ',-runtime/threadsafe_fn'
              ',-whitespace/newline'
              ]
 
 # http://pychecker.sourceforge.net/
-PYTHON_CHECKER = ['pychecker']
+PYTHON_CHECKER = ['pychecker', '-stdlib']
 
 RE_IGNORE = re.compile(r'@IGNORE_LINES_FOR_CODE_HYGIENE\[([0-9]+)\]')
 
 # ======================================================================
 def Debug(s):
   if VERBOSE:
     print s
 
 
 def RunCommand(cmd):
@@ skipping 482 matching lines @@
       num_error += 1
       continue
 
     errors, warnings = CheckFile(filename, True)
     if errors:
       num_error += 1
   return num_error
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))