Python readability review for dbeam@.

third_party/closure_compiler/compiler_customization_test.py

 #!/usr/bin/env python
 # Copyright 2014 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 os
 import unittest
 
 from checker import Checker
 from processor import FileCache, Processor
@@ skipping 18 matching lines @@
 
   def setUp(self):
     self._checker = Checker()
 
   def _runChecker(self, source_code):
     file_path = "/script.js"
     FileCache._cache[file_path] = source_code
     return self._checker.check(file_path)
 
   def _runCheckerTestExpectError(self, source_code, expected_error):
-    _, output = self._runChecker(source_code)
+    _, stderr = self._runChecker(source_code)
 
-    self.assertTrue(expected_error in output,
+    self.assertTrue(expected_error in stderr,
         msg="Expected chunk: \n%s\n\nOutput:\n%s\n" % (
-            expected_error, output))
+            expected_error, stderr))
 
   def _runCheckerTestExpectSuccess(self, source_code):
-    return_code, output = self._runChecker(source_code)
+    found_errors, stderr = self._runChecker(source_code)
 
-    self.assertTrue(return_code == 0,
-        msg="Expected success, got return code %d\n\nOutput:\n%s\n" % (
-            return_code, output))
+    self.assertFalse(found_errors,
+        msg="Expected success, but got failure\n\nOutput:\n%s\n" % stderr)
 
   def testGetInstance(self):
     self._runCheckerTestExpectError("""
 var cr = {
   /** @param {!Function} ctor */
   addSingletonGetter: function(ctor) {
     ctor.getInstance = function() {
       return ctor.instance_ || (ctor.instance_ = new ctor());
     };
   }
@@ skipping 172 matching lines @@
 function f() {
   var a = document.createElement('div');
   cr.ui.decorate(a, Class);
   return a;
 }
 """)
 
 
 if __name__ == "__main__":
   unittest.main()