Update docker-py

Using commit:
b31bb4d879

fig/packages/docker/errors.py

@@ -0,0 +1,61 @@
+#    Copyright 2014 dotCloud 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
+#
+#        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.
+
+import requests
+
+
+class APIError(requests.exceptions.HTTPError):
+    def __init__(self, message, response, explanation=None):
+        # requests 1.2 supports response as a keyword argument, but
+        # requests 1.1 doesn't
+        super(APIError, self).__init__(message)
+        self.response = response
+
+        self.explanation = explanation
+
+        if self.explanation is None and response.content:
+            self.explanation = response.content.strip()
+
+    def __str__(self):
+        message = super(APIError, self).__str__()
+
+        if self.is_client_error():
+            message = '%s Client Error: %s' % (
+                self.response.status_code, self.response.reason)
+
+        elif self.is_server_error():
+            message = '%s Server Error: %s' % (
+                self.response.status_code, self.response.reason)
+
+        if self.explanation:
+            message = '%s ("%s")' % (message, self.explanation)
+
+        return message
+
+    def is_client_error(self):
+        return 400 <= self.response.status_code < 500
+
+    def is_server_error(self):
+        return 500 <= self.response.status_code < 600
+
+
+class DockerException(Exception):
+    pass
+
+
+class InvalidRepository(DockerException):
+    pass
+
+
+class InvalidConfigFile(DockerException):
+    pass