fix/hush some flake8 warnings

test_ipaddrs.py had an invalid regexp, caught by the latest version of flake8

The new flake8 complains about both W503 (line break inside a conditional
before a binary operator) and W504 (line break *after* the operator). I think
break-before is the new preferred style, but for now I'm just going to ignore
them both and leave the code alone.

src/wormhole/test/test_ipaddrs.py

@@ -7,7 +7,7 @@ from twisted.trial import unittest
 
 from .. import ipaddrs
 
-DOTTED_QUAD_RE = re.compile("^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$")
+DOTTED_QUAD_RE = re.compile(r"^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$")
 
 MOCK_IPADDR_OUTPUT = """\
 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN \n\

tox.ini

@@ -42,6 +42,6 @@ deps = flake8
 commands = flake8 src/wormhole
 
 [flake8]
-ignore = E741
+ignore = E741,W503,W504
 exclude = .git,__pycache__,docs/source/conf.py,old,build,dist
 max-complexity = 40