render_pictures: add --mismatchPath flag

tools/tests/base_unittest.py

 #!/usr/bin/python
 
 """
 Copyright 2014 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 A wrapper around the standard Python unittest library, adding features we need
 for various unittests within this directory.
 """
 
+import errno
 import os
+import shutil
 import sys
 import unittest
 
 # Set the PYTHONPATH to include the tools directory.
 sys.path.append(
     os.path.join(os.path.dirname(os.path.realpath(__file__)), os.pardir))
 import find_run_binary
 
 
 class TestCase(unittest.TestCase):
 
   def shortDescription(self):
     """Tell unittest framework to not print docstrings for test cases."""
     return None
 
+  def create_empty_dir(self, path):
+    """Creates an empty directory at path and returns path.
+
+    Args:
+      path: path on local disk
+    """
+    shutil.rmtree(path=path, ignore_errors=True)
+    try:
+      os.makedirs(path)
+    except OSError as exc:
+      if exc.errno != errno.EEXIST:
+        raise
+    return path
+
   def run_command(self, args):
     """Runs a program from the command line and returns stdout.
 
     Args:
       args: Command line to run, as a list of string parameters. args[0] is the
             binary to run.
 
     Returns:
       stdout from the program, as a single string.
 
@@ skipping 24 matching lines @@
   context of run_all.py, which depends on that Exception to signal failures).
 
   TODO(epoger): Make all of our unit tests use the Python unittest framework,
   so we can leverage its ability to run *all* the tests and report failures at
   the end.
   """
   suite = unittest.TestLoader().loadTestsFromTestCase(test_case_class)
   results = unittest.TextTestRunner(verbosity=2).run(suite)
   if not results.wasSuccessful():
     raise Exception('failed unittest %s' % test_case_class)