Get run_test_cases.py to fail if it fails to get the list of tests it should run.

tools/isolate/run_test_cases_smoke_test.py

 #!/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.
 
 import logging
 import os
 import re
 import subprocess
 import sys
@@ skipping 81 matching lines @@
       re.escape(l) for l in gtest_fake_base.get_footer(1, 1).splitlines()
     ] + [
       '',
       re.escape('Success:    3 75.00%'),
       re.escape('Flaky:      0  0.00%'),
       re.escape('Fail:       1 25.00%'),
       r'\d+\.\ds Done running 4 tests with 6 executions. \d+\.\d test/s',
     ]
     self._check_results(expected_out_re, out, err)
 
+  def test_simple_gtest_list_error(self):
+    out, err, return_code = RunTest('gtest_fake_error.py')
+
+    expected_out_re = [
+        'Failed to run .+gtest_fake_error.py',
+        'Unable to list tests'
+    ]
+
+    self.assertEqual(1, return_code)
+    self._check_results(expected_out_re, out, err)
+
 
 if __name__ == '__main__':
   VERBOSE = '-v' in sys.argv
   logging.basicConfig(level=logging.DEBUG if VERBOSE else logging.ERROR)
   unittest.main()