Fix incorrectly resolved conflict, and add error message for missing sources.

ppapi/generators/idl_c_header.py

-#!/usr/bin/python
-#
+#!/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.
 
 """ Generator for C style prototypes and definitions """
 
 import glob
 import os
 import sys
 
@@ skipping 221 matching lines @@
   ast = ParseFiles(filenames)
   if hgen.GenerateRange(ast, ['M13', 'M14', 'M15'], {}):
     print "Golden file for M13-M15 failed."
     failed =1
   else:
     print "Golden file for M13-M15 passed."
 
   return failed
 
 if __name__ == '__main__':
-  retval = Main(sys.argv[1:])
-  sys.exit(retval)
+  sys.exit(Main(sys.argv[1:]))