Explicitly testing against Py3.5.2

Author: pavel-kirienko

.travis.yml

@@ -5,6 +5,7 @@ os:
   - linux   # Travis does not support Python on OSX or Windows. Should we migrate to a different CI service?
 
 python:
+  - '3.5.2'       # There have been compatibility issues with this patch version
   - '3.5'
   - '3.6'
   - '3.7-dev'     # TODO: Replace with plain "3.7" when supported by Travis