Updates the Shipyard error responses to match the modified structure

for undercloud component error structures. The primary modification is
the change from "errorList" to "messageList", and the addition of a
error boolean to each messageList record. The docstring for the default
error handler has been updated to further explain the relationship between
error and info messages and the default error message.

Change-Id: If91fee3cc1f59ff07c1b91eee11dc4f3d629bb0c

tests/unit/test_errors.py

@@ -0,0 +1,70 @@
+# Copyright 2017 AT&T Intellectual Property.  All other rights reserved.
+#
+# 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
+#
+#     http://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.
+from shipyard_airflow import errors
+
+
+def test_app_error():
+    """
+    test app error for status and title overrides
+    """
+
+    err = errors.AppError()
+    assert err.status == errors.AppError.status
+    assert err.title == errors.AppError.title
+
+    err = errors.AppError(title='Unfortunate News Everyone', status=999)
+    assert err.status == 999
+    assert err.title == 'Unfortunate News Everyone'
+
+
+def test_api_error():
+    """
+    test api error
+    """
+
+    err = errors.ApiError()
+    assert err.status == errors.ApiError.status
+    assert err.title == errors.ApiError.title
+
+    err = errors.ApiError(title='It was the worst of times', status=1)
+    assert err.title == 'It was the worst of times'
+    assert err.status == 1
+
+
+def test_database_error():
+    """
+    test database error
+    """
+
+    err = errors.DatabaseError()
+    assert err.status == errors.DatabaseError.status
+    assert err.title == errors.DatabaseError.title
+
+    err = errors.DatabaseError(title='Stuff Happens', status=1990)
+    assert err.status == 1990
+    assert err.title == 'Stuff Happens'
+
+
+def test_airflow_error():
+    """
+    test airflow error
+    """
+
+    err = errors.AirflowError()
+    assert err.status == errors.AirflowError.status
+    assert err.title == errors.AirflowError.title
+
+    err = errors.AirflowError(title='cron save us', status=500)
+    assert err.status == 500
+    assert err.title == 'cron save us'