Enabled hacking check H305

* [H305] imports not grouped correctly

Change-Id: I2b2bf2ca5d1a8cfa68169e11b8cb885172bad0a2

tests/test_functional.py

@@ -14,10 +14,10 @@
 #    under the License.
 
 import os
+import subprocess
 import sys
 
 import fixtures
-import subprocess
 import testtools
 from testtools import content
 

tox.ini

@@ -23,7 +23,6 @@ commands =
 commands = {posargs}
 
 [flake8]
-ignore = H305 
 show-source = True
 exclude = .tox,dist,doc,*.egg,build
 builtins = _