drain: adds __init__.py and cleanups flake8 nits

drain/drain.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 from pyln.client import Plugin, Millisatoshi, RpcError
-from utils import *
+from utils import get_ours, wait_ours
 import re
 import time
 import uuid
@@ -157,7 +157,7 @@ def test_or_set_chunks(plugin, payload):
             continue
         try:
             spend, recv = spendable_from_scid(plugin, payload, channel['short_channel_id'], True)
-        except RpcError as e:
+        except RpcError:
             continue
         channels[channel['short_channel_id']] = {
             'spendable': spend,

drain/test_drain.py

@@ -1,14 +1,16 @@
-from pyln.testing.fixtures import *
+from pyln.testing.fixtures import *  # noqa: F401,F403
 from pyln.testing.utils import DEVELOPER
-from pyln.client import RpcError, Millisatoshi
-from utils import *
+from pyln.client import RpcError
+from .utils import get_ours, get_theirs, wait_ours, wait_for_all_htlcs
 import os
 import unittest
+import pytest
 
 
 pluginopt = {'plugin': os.path.join(os.path.dirname(__file__), "drain.py")}
 EXPERIMENTAL_FEATURES = int(os.environ.get("EXPERIMENTAL_FEATURES", "0"))
 
+
 @unittest.skipIf(not DEVELOPER, "slow gossip, needs DEVELOPER=1")
 def test_drain_and_refill(node_factory, bitcoind):
     # Scenario: first drain then refill