Fix some pep8 warnings

Fix some pep8 warnings found running under python3.5.

Also removed some ignore directives that were carried
over from the neutron tree, and exclude some additional
directories.

Trivialfix

Change-Id: I96f53d3d142352f0d2c7cc641391019b476b0724
diff --git a/neutron_tempest_plugin/api/test_timestamp.py b/neutron_tempest_plugin/api/test_timestamp.py
index 4d2d32a..769d7cc 100644
--- a/neutron_tempest_plugin/api/test_timestamp.py
+++ b/neutron_tempest_plugin/api/test_timestamp.py
@@ -27,7 +27,7 @@
 
     required_extensions = ["standard-attr-timestamp"]
 
-    ## attributes for subnetpool
+    # attributes for subnetpool
     min_prefixlen = '28'
     max_prefixlen = '31'
     _ip_version = 4