Update from https://crrev.com/312398

build/android/pylib/utils/findbugs.py

 # 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.
 
 import optparse
 import os
 import re
 import shlex
 import subprocess
 import sys
@@ skipping 14 matching lines @@
     print '-' * 80
     print
 
 
 def _StripLineNumbers(current_warnings):
   re_line = r':\[line.*?\]$'
   return [re.sub(re_line, '', x) for x in current_warnings]
 
 
 def _DiffKnownWarnings(current_warnings_set, known_bugs_file):
-  with open(known_bugs_file, 'r') as known_bugs:
-    known_bugs_set = set(known_bugs.read().splitlines())
+  if os.path.exists(known_bugs_file):
+    with open(known_bugs_file, 'r') as known_bugs:
+      known_bugs_set = set(known_bugs.read().splitlines())
+  else:
+    known_bugs_set = set()
 
   new_warnings = current_warnings_set - known_bugs_set
   _PrintMessage(sorted(new_warnings), 'New', 'Please fix, or perhaps add to',
                 known_bugs_file)
 
   obsolete_warnings = known_bugs_set - current_warnings_set
   _PrintMessage(sorted(obsolete_warnings), 'Obsolete', 'Please remove from',
                 known_bugs_file)
 
   count = len(new_warnings) + len(obsolete_warnings)
@@ skipping 196 matching lines @@
 
 def main():
   parser = GetCommonParser()
   options, _ = parser.parse_args()
 
   return Run(options)
 
 
 if __name__ == '__main__':
   sys.exit(main())