[Findit] Add a sub-pipeline to detect first-known failure.

appengine/findit/waterfall/base_pipeline.py

+# 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.
+
+from pipeline_utils import pipelines
+
+
+# TODO(stgao): remove BasePipeline after http://crrev.com/810193002 is landed.
+class BasePipeline(pipelines.AppenginePipeline):  # pragma: no cover
+  def run_test(self, *args, **kwargs):
+    pass
+
+  def finalized_test(self, *args, **kwargs):
+    pass
+
+  def callback(self, **kwargs):
+    pass
+
+  def run(self, *args, **kwargs):
+    raise NotImplementedError()