Fix pytest-cov spec for Py3.4

Author: wsanchez

tox.ini

@@ -58,7 +58,7 @@ deps =
     # For code coverage
     {[testenv:coverage_report]deps}
     py{26,27,34,py2}: pytest-cov==2.8.1  # rq.filter: <2.9
-    py{34,35,36,37,38,39,py3}: pytest-cov==2.10.0
+    py{35,36,37,38,39,py3}: pytest-cov==2.10.0
 
     # For hypothesis. Note Python 3.4 isn't supported by hypothesis.
     py{26,27,py2}: hypothesis==4.43.9  # rq.filter: <4.44