Shame on you, Ursula.

nucypher/characters/lawful.py

@@ -66,8 +66,6 @@ from nucypher.network.nodes import Teacher
 from nucypher.network.protocols import InterfaceInfo, parse_node_uri
 from nucypher.network.server import ProxyRESTServer, TLSHostingPower, make_rest_app
 from nucypher.utilities.decorators import validate_checksum_address
-# TODO: Fix circular import issue
-#from nucypher.policy.models import UnquestionableEvidence
 
 
 class Alice(Character, PolicyAuthor):
@@ -552,10 +550,9 @@ class Bob(Character):
             except UmbralCorrectnessError:
                 evidence = self.collect_evidence(capsule=capsule,
                                                  cfrag=cfrag,
-                                                 )
+                                                 ursula=work_order.ursula)
                 # TODO: Here's the evidence of Ursula misbehavior. Now what? #500
                 raise self.IncorrectCFragReceived(evidence)
-
         else:
             raise Ursula.NotEnoughUrsulas("Unable to snag m cfrags.")
 
@@ -567,10 +564,9 @@ class Bob(Character):
         cleartexts.append(delivered_cleartext)
         return cleartexts
 
-    def collect_evidence(self, capsule, cfrag):
-        pass
-        # TODO: Fix circular import problem
-        # return UnquestionableEvidence(capsule, cfrag)
+    def collect_evidence(self, capsule, cfrag, ursula):
+        from nucypher.policy.models import UnquestionableEvidence
+        return UnquestionableEvidence(capsule, cfrag, ursula)
 
 def make_wsgi_app(drone_bob, start_learning=True):
         bob_control = Flask('bob-control')

nucypher/policy/models.py

@@ -681,9 +681,10 @@ class Revocation:
 
 class UnquestionableEvidence:
 
-    def __init__(self, capsule: Capsule, cfrag: CapsuleFrag) -> None:
+    def __init__(self, capsule: Capsule, cfrag: CapsuleFrag, ursula) -> None:
         self.capsule = capsule
         self.cfrag = cfrag
+        self.ursula = ursula
 
     def get_proof_challenge_scalar(self) -> CurveBN:
         umbral_params = default_params()

tests/blockchain/eth/contracts/main/mining_adjudicator/test_mining_adjudicator.py

@@ -125,7 +125,7 @@ def test_evaluate_cfrag(testerchain, escrow, adjudicator_contract):
     cfrag_bytes = cfrag.to_bytes()
 
     # Bob prepares supporting Evidence
-    evidence = UnquestionableEvidence(capsule, cfrag)
+    evidence = UnquestionableEvidence(capsule, cfrag, ursula=None)
 
     some_data = evidence.precompute_values()
     assert len(some_data) == 20 * 32