dm: decode bytestring

Thanks: Alexandre Detiste <alexandre.detiste@gmail.com> for reporting
Signed-off-by: Mattia Rizzolo <mattia@debian.org>

dm/tests/test_claim.py

@@ -71,7 +71,7 @@ class TestClaim(PersonFixtureMixin, TestCase):
 
         # Get and return the confirmation url from the result
         self.assertIn("/dm/claim/confirm", response.context["plaintext"])
-        self.assertIn(b"-----BEGIN PGP MESSAGE-----", response.context["challenge"])
+        self.assertIn("-----BEGIN PGP MESSAGE-----", response.context["challenge"])
         return identity, response.context["plaintext"].strip()
 
     def _test_success(self, person, issuer):

dm/views.py

@@ -104,7 +104,7 @@ class Claim(VisitorMixin, FormView):
             # by unit tests without the need to have access to the private key
             # to decode it
             ctx["plaintext"] = plaintext
-            ctx["challenge"] = key.encrypt(plaintext.encode("utf8"))
+            ctx["challenge"] = key.encrypt(plaintext.encode("utf8")).decode("utf8")
         return ctx
 
     def form_valid(self, form):