Use a subprocess wrapper that will throw if a command returns a non-zero result code

autotest.py

 #!/usr/bin/env python
 # coding: utf-8
 
 # This Source Code is subject to the terms of the Mozilla Public License
 # version 2.0 (the "License"). You can obtain a copy of the License at
 # http://mozilla.org/MPL/2.0/.
 
 import sys, os, subprocess, re, difflib, utils
 
 def run_tests():
@@ skipping 17 matching lines @@
       if match and match.group(1).lower() == 'name':
         name = match.group(2)
       elif match and match.group(1).lower() == 'arguments':
         arguments = match.group(2).split(' ')
     handle.close()
 
     if arguments == None:
       continue
 
     command = [application, os.path.join(baseDir, 'jshydra.js'), file] + arguments
-    out = subprocess.check_output(command, env=env).replace('\r', '')
+    out = subprocess.check_output(command, stderr=subprocess.STDOUT, env=env).replace('\r', '')
     expected = open(file + '.expected', 'r').read().replace('\r', '')
     if out == expected:
       print '%s passed' % name
     else:
       print '%s failed! Log:' % name
       for line in difflib.unified_diff(expected.split('\n'), out.split('\n'), fromfile=file + '.expected', tofile=file + '.output'):
         print line
       print
 
 if __name__ == '__main__':
   run_tests()