Import only modules and update tox.ini

As stated in the OpenStack Hacking Guidelines, it is prefered
that only modules should be imported.

Also updated tox.ini to ignore opestack/common among others.

Change-Id: I2f0a603c31052eadee581c11880c0ec6bd392829

tox.ini

@@ -37,7 +37,6 @@ downloadcache = ~/cache/pip
 
 [flake8]
 # H233  Python 3.x incompatible use of print operator
-# H302  import only modules
 # H303  no wildcard import
 # H404  multi line docstring should start with a summary
 
@@ -49,6 +48,9 @@ downloadcache = ~/cache/pip
 # H238  old style class declaration, use new style (inherit from `object`)
 # E128  continuation line under-indented for visual indent
 
-ignore = F403,F812,F821,H233,H302,H303,H404,E265,H405,E123,H238,E128
+ignore = F403,F812,F821,H233,H303,H404,E265,H405,E123,H238,E128
 show-source = True
-exclude = .venv,.tox,dist,*egg,build
+exclude = .venv*,.tox,dist,*egg,build,.git,doc,*openstack/common*,*lib/python*,.update-venv
+
+[hacking]
+import_exceptions = six.moves