Resolve discrepancy with NotEnoughNodes exceptions; preserve discription of multi inheretance

nucypher/blockchain/eth/actors.py

@@ -270,6 +270,7 @@ class PolicyAuthor(NucypherTokenActor):
 
         if policy_agent is None:
             # From defaults
+            self.token_agent = NucypherTokenAgent()
             self.miner_agent = MinerAgent(token_agent=self.token_agent)
             self.policy_agent = PolicyAgent(miner_agent=self.miner_agent)
         else:

nucypher/characters/base.py

@@ -21,7 +21,6 @@ from typing import Union, List
 from umbral.keys import UmbralPublicKey
 from umbral.signing import Signature
 
-from nucypher.blockchain.eth.agents import MinerAgent
 from nucypher.crypto.api import encrypt_and_sign
 from nucypher.crypto.kits import UmbralMessageKit
 from nucypher.crypto.powers import CryptoPower, SigningPower, EncryptingPower, NoSigningPower, CryptoPowerUp
@@ -321,12 +320,6 @@ class Character(Learner):
 
     from nucypher.network.protocols import SuspiciousActivity  # Ship this exception with every Character.
 
-    class NotEnoughUrsulas(MinerAgent.NotEnoughMiners):
-        """
-        All Characters depend on knowing about enough Ursulas to perform their role.
-        This exception is raised when a piece of logic can't proceed without more Ursulas.
-        """
-
     class InvalidSignature(Exception):
         """
         Raised when a signature doesn't pass validation/verification.

nucypher/characters/lawful.py

@@ -242,7 +242,7 @@ class Bob(Character):
         if not self.known_nodes and not self._learning_task.running:
             # Quick sanity check - if we don't know of *any* Ursulas, and we have no
             # plans to learn about any more, than this function will surely fail.
-            raise self.NotEnoughUrsulas
+            raise Ursula.NotEnoughUrsulas
 
         treasure_map = self.get_treasure_map_from_known_ursulas(self.network_middleware,
                                                                 map_id)
@@ -387,6 +387,12 @@ class Ursula(Character, VerifiableNode, Miner):
     # TLSHostingPower still can enjoy default status, but on a different class
     _default_crypto_powerups = [SigningPower, EncryptingPower]
 
+    class NotEnoughUrsulas(Learner.NotEnoughTeachers, MinerAgent.NotEnoughMiners):
+        """
+        All Characters depend on knowing about enough Ursulas to perform their role.
+        This exception is raised when a piece of logic can't proceed without more Ursulas.
+        """
+
     class NotFound(Exception):
         pass