From ab98d5c39fc19cc90785a87f10cc4b53390e8b20 Mon Sep 17 00:00:00 2001
From: Richard Barnes <rlb@ipv.sx>
Date: Mon, 28 Sep 2015 17:14:33 -0400
Subject: [PATCH] Ignore unknown challenge types

---
 acme/acme/messages.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/acme/acme/messages.py b/acme/acme/messages.py
index 02ae24c8f..002c08767 100644
--- a/acme/acme/messages.py
+++ b/acme/acme/messages.py
@@ -373,7 +373,17 @@ class Authorization(ResourceBody):
 
     @challenges.decoder
     def challenges(value):  # pylint: disable=missing-docstring,no-self-argument
-        return tuple(ChallengeBody.from_json(chall) for chall in value)
+        # 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 = []
+        for chall in value:
+            try:
+                challenges.append(ChallengeBody.from_json(chall))
+            except errors.UnknownTypeError:
+                continue
+        return tuple(challenges)
 
     @property
     def resolved_combinations(self):