Fix pylint and add test

acme/acme/messages.py

@@ -2,6 +2,7 @@
 import collections
 
 from acme import challenges
+from acme import errors
 from acme import fields
 from acme import jose
 from acme import util
@@ -373,17 +374,17 @@ class Authorization(ResourceBody):
 
     @challenges.decoder
     def challenges(value):  # pylint: disable=missing-docstring,no-self-argument
-        # The from_json method raises errors.UnrecognizedTypeError when a 
+        # The from_json method raises errors.UnrecognizedTypeError when a
         # challenge of unknown type is encountered.  We want to ignore this
         # case.  This forces us to do an explicit iteration, since list
         # comprehensions can't handle exceptions.
-        challenges = []
+        challs = []
         for chall in value:
             try:
-                challenges.append(ChallengeBody.from_json(chall))
-            except errors.UnknownTypeError:
+                challs.append(ChallengeBody.from_json(chall))
+            except jose.UnrecognizedTypeError:
                 continue
-        return tuple(challenges)
+        return tuple(challs)
 
     @property
     def resolved_combinations(self):

acme/acme/messages_test.py

@@ -274,6 +274,9 @@ class AuthorizationTest(unittest.TestCase):
     def setUp(self):
         from acme.messages import ChallengeBody
         from acme.messages import STATUS_VALID
+
+        unknown_chall = mock.MagicMock()
+        unknown_chall.to_json.side_effect = side_effect=jose.UnrecognizedTypeError
         self.challbs = (
             ChallengeBody(
                 uri='http://challb1', status=STATUS_VALID,
@@ -300,6 +303,19 @@ class AuthorizationTest(unittest.TestCase):
             'combinations': combinations,
         }
 
+        # For unknown challenge types
+        self.jmsg_unknown_chall = {
+            'resource': 'challenge',
+            'uri': 'random_uri',
+            'type': 'unknown',
+            'tls': True,
+        }
+
+        self.jobj_from_unknown = {
+            'identifier': identifier.to_json(),
+            'challenges': [self.jmsg_unknown_chall],
+        }
+
     def test_from_json(self):
         from acme.messages import Authorization
         Authorization.from_json(self.jobj_from)
@@ -314,6 +330,11 @@ class AuthorizationTest(unittest.TestCase):
             (self.challbs[1], self.challbs[2]),
         ))
 
+    def test_unknown_chall_type(self):
+        """Just make sure an error isn't thrown."""
+        from acme.messages import Authorization
+        Authorization.from_json(self.jobj_from_unknown)
+
 
 class AuthorizationResourceTest(unittest.TestCase):
     """Tests for acme.messages.AuthorizationResource."""