Fix missing 'UnknownMessage' exception

The recent 1.7 version of pylint moved the exceptions to a different
submodule and this ensures everything works as expected.

prospector/exceptions.py

@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
-
+try:
+    from pylint.utils import UnknownMessage as UnknownMessageError
+except ImportError:
+    from pylint.exceptions import UnknownMessageError
 
 class FatalProspectorException(Exception):
 

prospector/tools/pylint/__init__.py

@@ -4,7 +4,7 @@
 import sys
 import os
 from pylint.config import find_pylintrc
-from pylint.utils import UnknownMessage
+from prospector.exceptions import UnknownMessageError
 from prospector.message import Message, Location
 from prospector.tools.base import ToolBase
 from prospector.tools.pylint.collector import Collector
@@ -41,7 +41,7 @@ def _prospector_configure(self, prospector_config, linter):
             try:
                 linter.disable(msg_id)
             # pylint: disable=pointless-except
-            except UnknownMessage:
+            except UnknownMessageError:
                 # If the msg_id doesn't exist in PyLint any more,
                 # don't worry about it.
                 pass

prospector/tools/pylint/collector.py

@@ -1,6 +1,6 @@
 from __future__ import absolute_import
 from pylint.reporters import BaseReporter
-from pylint.utils import UnknownMessage
+from prospector.exceptions import UnknownMessageError
 from prospector.message import Location, Message
 
 
@@ -20,7 +20,7 @@ def add_message(self, msg_id, location, msg):
         # more user-friendly symbol
         try:
             msg_data = self._message_store.check_message_id(msg_id)
-        except UnknownMessage:
+        except UnknownMessageError:
             # this shouldn't happen, as all pylint errors should be
             # in the message store, but just in case we'll fall back
             # to using the code.