# Buggy code
def validate_worker(self, verify_staking: bool = True) -> None:
    # Federated
    if self.federated_only:
        message = (
            "This node cannot be verified in this manner, "
            "but is OK to use in federated mode if you "
            "have reason to believe it is trustworthy."
        )
        raise self.WrongMode(message)

    # Decentralized
    else:
        if self.__decentralized_identity_evidence is NOT_SIGNED:
            raise self.StampNotSigned

        # Off-chain signature verification
        if not self._stamp_has_valid_signature_by_worker():
            message = (
                f"Invalid signature {self.__decentralized_identity_evidence.hex()} "
                f"from worker {self.worker_address} for stamp {bytes(self.stamp).hex()} "
            )
            raise self.InvalidWorkerSignature(message)

        # On-chain staking check
        if verify_staking:
            if not self._worker_is_bonded_to_staker():  # <-- Blockchain CALL
                message = f"Worker {self.worker_address} is not bonded to staker {self.checksum_address}"
                raise self.DetachedWorker(message)

            if self._staker_is_really_staking():  # <-- Blockchain CALL
                self.verified_worker = True
            else:
                raise self.NotStaking(f"Staker {self.checksum_address} is not staking")

        self.verified_stamp = True


# Traceback (ValueError)
$ nucypher ursula confirm-activity



,ggg,         gg
dP""Y8a        88                                   ,dPYb,
Yb, `88        88                                   IP'`Yb
`"  88        88                                   I8  8I
88        88                                   I8  8'
88        88   ,gggggg,    ,g,     gg      gg  I8 dP    ,gggg,gg
88        88   dP""""8I   ,8'8,    I8      8I  I8dP    dP"  "Y8I
88        88  ,8'    8I  ,8'  Yb   I8,    ,8I  I8P    i8'    ,8I
Y8b,____,d88,,dP     Y8,,8'_   8) ,d8b,  ,d8b,,d8b,_ ,d8,   ,d8b,
"Y888888P"Y88P      `Y8P' "YY8P8P8P'"Y88P"`Y88P'"Y88P"Y8888P"`Y8


the Untrusted Re-Encryption Proxy.


Decrypting NuCypher keyring...
WARNING - No Bootnodes Available
Traceback (most recent call last):
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/bin/nucypher", line 11, in <module>
load_entry_point('nucypher', 'console_scripts', 'nucypher')()
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/decorators.py", line 64, in new_func
return ctx.invoke(f, obj, *args, **kwargs)
File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/ubuntu/nucypher/nucypher/cli/config.py", line 219, in wrapper
return func(config, *args, **kwargs)
File "/home/ubuntu/nucypher/nucypher/cli/characters/ursula.py", line 268, in ursula
client_password=client_password)
File "/home/ubuntu/nucypher/nucypher/cli/actions.py", line 288, in make_cli_character
**config_args)
File "/home/ubuntu/nucypher/nucypher/config/node.py", line 215, in __call__
return self.produce(**character_kwargs)
File "/home/ubuntu/nucypher/nucypher/config/characters.py", line 103, in produce
merged_parameters = self.generate_parameters(**overrides)
File "/home/ubuntu/nucypher/nucypher/config/node.py", line 284, in generate_parameters
merged_parameters = {**self.static_payload(), **self.dynamic_payload, **overrides}
File "/home/ubuntu/nucypher/nucypher/config/characters.py", line 98, in dynamic_payload
return {**super().dynamic_payload, **payload}
File "/home/ubuntu/nucypher/nucypher/config/node.py", line 385, in dynamic_payload
self.read_known_nodes()   # Requires a connected blockchain to init Ursulas.
File "/home/ubuntu/nucypher/nucypher/config/node.py", line 260, in read_known_nodes
known_nodes = self.node_storage.all(federated_only=self.federated_only)
File "/home/ubuntu/nucypher/nucypher/config/storages.py", line 415, in all
federated_only=federated_only)  # TODO: 466
File "/home/ubuntu/nucypher/nucypher/config/storages.py", line 384, in __read_metadata
node = Ursula.from_bytes(node_bytes, registry=registry, federated_only=federated_only)
File "/home/ubuntu/nucypher/nucypher/characters/lawful.py", line 1175, in from_bytes
ursula = cls.from_public_keys(registry=registry, federated_only=federated_only, **node_info)
File "/home/ubuntu/nucypher/nucypher/characters/base.py", line 310, in from_public_keys
return cls(is_me=False, federated_only=federated_only, crypto_power=crypto_power, *args, **kwargs)
File "/home/ubuntu/nucypher/nucypher/characters/lawful.py", line 831, in __init__
**character_kwargs)
File "/home/ubuntu/nucypher/nucypher/characters/base.py", line 116, in __init__
raise ValueError(f"Pass either federated only or registry.  Got '{federated_only}'. '{registry}'")
ValueError: Pass either federated only or registry.  Got 'None'. 'None'
Sentry is attempting to send 0 pending error messages
Waiting up to 2.0 seconds
Press Ctrl-C to quit

# Fixed code
def validate_worker(self, registry: BaseContractRegistry = None) -> None:
    # Federated
    if self.federated_only:
        message = (
            "This node cannot be verified in this manner, "
            "but is OK to use in federated mode if you "
            "have reason to believe it is trustworthy."
        )
        raise self.WrongMode(message)

    # Decentralized
    else:
        if self.__decentralized_identity_evidence is NOT_SIGNED:
            raise self.StampNotSigned

        # Off-chain signature verification
        if not self._stamp_has_valid_signature_by_worker():
            message = (
                f"Invalid signature {self.__decentralized_identity_evidence.hex()} "
                f"from worker {self.worker_address} for stamp {bytes(self.stamp).hex()} "
            )
            raise self.InvalidWorkerSignature(message)

        # On-chain staking check, if registry is present
        if registry:
            if not self._worker_is_bonded_to_staker(
                registry=registry
            ):  # <-- Blockchain CALL
                message = f"Worker {self.worker_address} is not bonded to staker {self.checksum_address}"
                raise self.DetachedWorker(message)

            if self._staker_is_really_staking(registry=registry):  # <-- Blockchain CALL
                self.verified_worker = True
            else:
                raise self.NotStaking(f"Staker {self.checksum_address} is not staking")

        self.verified_stamp = True