Make blink_trybot recipe work on windows

scripts/slave/unittests/recipe_configs_test.py

 #!/usr/bin/python
 # Copyright 2013 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.
 
 """Provides test coverage for common recipe configurations.
 
 recipe config expectations are located in ../recipe_configs_test/*.expected
 
 In training mode, this will loop over every config item in ../recipe_configs.py
@@ skipping 70 matching lines @@
         return file_name, None, None
 
     for config_name, fn in ctx.CONFIG_ITEMS.iteritems():
       if fn.NO_TEST or fn.IS_ROOT:
         continue
       try:
         result = covered(fn, make_item())
         if result.complete():
           ret[config_name] = result.as_jsonish()
       except recipe_configs_util.BadConf, e:
-        ret[config_name] = e.message
+        ret[config_name] = str(e)
     return file_name, (ctx.TEST_NAME_FORMAT % var_assignments), ret
   except Exception, e:
     print 'Caught exception [%s] with args %s: %s' % (e, args, config_name)
 
 
 def train_from_tests(args):
   file_name, _, configuration_results = evaluate_configurations(args)
   if configuration_results is not None:
     if configuration_results:
       print 'Writing', file_name
-      with open(file_name, 'w') as f:
+      with open(file_name, 'wb') as f:
         json.dump(configuration_results, f, sort_keys=True, indent=2)
     else:
       print 'Empty', file_name
 
   if not configuration_results:  # None or {}
     if os.path.exists(file_name):
       os.unlink(file_name)
   return True
 
 
 def load_tests(loader, _standard_tests, _pattern):
   """This method is invoked by unittest.main's automatic testloader."""
   def create_test_class(args):
     file_name, test_name_suffix, configuration_results = args
     if configuration_results is None:
       return
 
     json_expectation = {}
     if os.path.exists(file_name):
-      with open(file_name, 'r') as f:
+      with open(file_name, 'rb') as f:
         json_expectation = json.load(f)
 
     class RecipeConfigsTest(unittest.TestCase):
       def testNoLeftovers(self):
         """add_test_methods() should completely drain json_expectation."""
         self.assertEqual(json_expectation, {})
 
       @classmethod
       def add_test_methods(cls):
         for name, result in configuration_results.iteritems():
@@ skipping 13 matching lines @@
 
   suite = unittest.TestSuite()
   for test_class in map(create_test_class, data):
     if test_class is None:
       continue
     suite.addTest(loader.loadTestsFromTestCase(test_class))
   return suite
 
 
 def multiprocessing_init():
-  # HACK: multiprocessing doesn't work with atexit, so shim os._exit instead.
-  # This allows us to save exactly one coverage file per subprocess
+  init_recipe_modules()
+
+  # HACK: multiprocessing doesn't work with atexit, so shim the exit functions
+  # instead. This allows us to save exactly one coverage file per subprocess.
   # pylint: disable=W0212
-  init_recipe_modules()
-  real_os_exit = os._exit
+  real_os_exit = multiprocessing.forking.exit
   def exitfn(code):
     COVERAGE.save()
     real_os_exit(code)
-  os._exit = exitfn
+  multiprocessing.forking.exit = exitfn
+
+  # This check mirrors the logic in multiprocessing.forking.exit
+  if sys.platform != 'win32':
+    # Even though multiprocessing.forking.exit is defined, it's not used in the
+    # non-win32 version multiprocessing.forking.Popen... *loss for words*
+    os._exit = exitfn
 
 
 def coverage_parallel_map(fn):
   combination_generator = (
     (mod_id, var_assignments)
     for mod_id, mod in RECIPE_MODULES.__dict__.iteritems()
       if mod_id[0] != '_' and mod.CONFIG_CTX
     for var_assignments in imap(dict, product(*[
       [(key_name, val) for val in vals]
       for key_name, vals in mod.CONFIG_CTX.VAR_TEST_MAP.iteritems()
@@ skipping 48 matching lines @@
     total_covered = COVERAGE.report()
     if total_covered != 100.0:
       print 'FATAL: Recipes configs are not at 100% coverage.'
       retcode = retcode or 2
 
   return retcode
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))