message: Add an option in upgrade script to not output when error happens
diff: @@ -899,12 +899,13 @@ class ASTCodeUpgrader(object):
  type(api_change_spec))
  self._api_change_spec = api_change_spec
  - def process_file(self, in_filename, out_filename):
  + def process_file(self, in_filename, out_filename, no_out_on_error=False):
  """Process the given python file for incompatible changes.
  Args:
  in_filename: filename to parse
  out_filename: output file to write to
  + no_out_on_error: do not modify the output file when errors happen
  Returns:
  A tuple representing number of files processed, log of actions, errors
  """
  @@ -917,6 +918,9 @@ class ASTCodeUpgrader(object):
  temp_file)
  # pylint: enable=g-backslash-continuation
  + if no_out_on_error and ret[-1]:
  + os.remove(temp_file.name)
  + else:
  shutil.move(temp_file.name, out_filename)
  return ret
  