Add a lightweight errors module.

ffn/inference/errors.py

@@ -0,0 +1,20 @@
+# Copyright 2018 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Exceptions for FFN inference."""
+
+
+class TerminationException(Exception):  # pylint: disable=g-bad-exception-name
+  """Indicates that the program has been requested to shut down."""
+  pass

ffn/inference/executor.py

@@ -39,14 +39,10 @@
 
 from ..training import model as ffn_model
 from . import inference_utils
+from .errors import TerminationException
 from .inference_utils import timer_counter
 
 
-class TerminationException(Exception):  # pylint: disable=g-bad-exception-name
-  """Indicates that the program has been requested to shut down."""
-  pass
-
-
 class ExecutorInterface:
   """Provides a client/server interface.