omit coveralls when flake8 runs

.travis.yml

@@ -8,4 +8,4 @@ install:
 script: tox -e $TOX_ENV
 after_success: 
   - pip install coveralls
-  - coveralls
+  - python {toxinidir}/run_coveralls.py

run_coveralls.py

@@ -0,0 +1,11 @@
+#!/bin/env/python
+import os
+from subprocess import call
+
+
+if __name__ == '__main__':
+    travis = 'TRAVIS' in os.environ
+    py35 = os.environ.get('TOX_ENV') == 'py35'
+
+    if travis and py35:
+        raise SystemExit(call('coveralls'))