First pass at an interactive CLI tool for interacting with agents

TODO: Find a better location for this script?

scripts/hooks/nucypher_agents.py

@@ -0,0 +1,61 @@
+# Get an interactive Python session with all the NuCypher agents loaded by running:
+#    python -i scripts/hooks/nucypher_agents.py <NETWORK> <PROVIDER_URI>
+
+import sys
+import os
+
+from nucypher.blockchain.eth.agents import ContractAgency, StakingEscrowAgent, PolicyManagerAgent, NucypherTokenAgent
+from nucypher.config.constants import NUCYPHER_ENVVAR_PROVIDER_URI
+from nucypher.blockchain.eth.interfaces import BlockchainInterfaceFactory
+from nucypher.blockchain.eth.registry import InMemoryContractRegistry
+
+from nucypher.characters.control.emitters import StdoutEmitter
+from nucypher.utilities.logging import GlobalLoggerSettings
+
+from constant_sorrow.constants import NO_BLOCKCHAIN_CONNECTION
+from eth_utils import to_checksum_address
+
+
+NO_BLOCKCHAIN_CONNECTION.bool_value(False)  # FIXME
+
+GlobalLoggerSettings.start_console_logging()
+
+emitter = StdoutEmitter(verbosity=2)
+
+try:
+    provider_uri = sys.argv[2]
+except IndexError:
+    provider_uri = os.getenv(NUCYPHER_ENVVAR_PROVIDER_URI)
+    if not provider_uri:
+        emitter.message("You have to pass a provider URI", color='red')
+        sys.exit(-1)
+
+try:
+    network = sys.argv[1]
+except IndexError:
+    network = "cassandra"
+
+
+BlockchainInterfaceFactory.initialize_interface(provider_uri=provider_uri,
+                                                poa=True,
+                                                light=False,
+                                                sync=False,
+                                                emitter=emitter)
+
+blockchain = BlockchainInterfaceFactory.get_interface(provider_uri=provider_uri)
+
+emitter.echo(message="Reading Latest Chaindata...")
+blockchain.connect()
+
+registry = InMemoryContractRegistry.from_latest_publication(network=network)
+
+emitter.echo(f"NOTICE: Connecting to {network} network", color='yellow')
+
+staking_agent = ContractAgency.get_agent(agent_class=StakingEscrowAgent, registry=registry)  # type: StakingEscrowAgent
+policy_agent = ContractAgency.get_agent(agent_class=PolicyManagerAgent, registry=registry)  # type: PolicyManagerAgent
+token_agent = ContractAgency.get_agent(agent_class=NucypherTokenAgent, registry=registry)  # type: NucypherTokenAgent
+
+
+emitter.echo(message=f"Current period: {staking_agent.get_current_period()}", color='yellow')
+emitter.echo(message=f"NuCypher agents pre-loaded in variables 'staking_agent', 'policy_agent', and 'token_agent'",
+             color='green')