Update out-of-date references to fake_repository.py

mojo/tools/testing/mojom_fetcher/repository_tests.py

 # Copyright 2015 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 io
 import os.path
 import unittest
 
 from fetcher.dependency import Dependency
 
 # Fake repository for testing
-from fake_repository import FakeRepository
+from fakes import FakeRepository
 
 
 class TestRepository(unittest.TestCase):
   def test_init(self):
     repository = FakeRepository("/path/to/repo", "third_party/external")
     self.assertEqual("/path/to/repo", repository.get_repo_root_directory())
     self.assertEqual("/path/to/repo/third_party/external",
                      repository.get_external_directory())
 
   def test_get_missing_dependencies(self):
@@ skipping 11 matching lines @@
     self.assertEquals([Dependency(repository,
         "/path/to/repo/third_party/external/services.domokit.org/foo/fiz.mojom",
         "services.fiz.org/foo/bar.mojom")], missing_deps)
 
   def test_get_external_urls(self):
     repository = FakeRepository("/path/to/repo", "third_party/external")
     urls = repository.get_external_urls()
     self.assertEquals(["/path/to/repo/third_party/external"],
                       repository.directories_walked)
     self.assertEquals(["services.domokit.org/foo/fiz.mojom"], urls)