Ignore E402 in PyFlakes

The lint warning is not appropriate as not all imports can be placed at the top of files.

src/sentry/wsgi.py:19:1: E402 module level import not at top of file
src/sentry/wsgi.py:22:1: E402 module level import not at top of file
src/sentry/wsgi.py:30:1: E402 module level import not at top of file
src/sentry/wsgi.py:31:1: E402 module level import not at top of file
src/sentry/api/client.py:5:1: E402 module level import not at top of file
src/sentry/api/client.py:6:1: E402 module level import not at top of file

setup.cfg

@@ -4,7 +4,7 @@ addopts=--tb=native
 norecursedirs=bin dist docs	htmlcov script hooks node_modules .* {args}
 
 [flake8]
-ignore = F999,E501,E128,E124,F841
+ignore = F999,E501,E128,E124,E402,F841
 max-line-length = 100
 exclude = .tox,.git,*/migrations/*,src/sentry/static/sentry/vendor/*,docs/*