Put in dummy challenge

acme/acme/challenges.py

@@ -34,6 +34,11 @@ class DVChallenge(Challenge):  # pylint: disable=abstract-method
     """Domain validation challenges."""
 
 
+class UnrecognizedChallenge(DVChallenge):
+    """Unrecognized challenge."""
+    typ = "unknown"
+
+
 class ChallengeResponse(jose.TypedJSONObjectWithFields):
     # _fields_to_partial_json | pylint: disable=abstract-method
     """ACME challenge response."""

acme/acme/messages.py

@@ -2,7 +2,6 @@
 import collections
 
 from acme import challenges
-from acme import errors
 from acme import fields
 from acme import jose
 from acme import util
@@ -383,7 +382,9 @@ class Authorization(ResourceBody):
             try:
                 challs.append(ChallengeBody.from_json(chall))
             except jose.UnrecognizedTypeError:
-                continue
+                challs.append(ChallengeBody(
+                    uri="UNKNOWN", chall=challenges.UnrecognizedChallenge,
+                    status=STATUS_UNKNOWN))
         return tuple(challs)
 
     @property

acme/acme/messages_test.py

@@ -275,8 +275,6 @@ class AuthorizationTest(unittest.TestCase):
         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,