Try to fix circleci coverage

.circleci/config.yml

@@ -42,7 +42,7 @@ jobs:
       - run:
           name: run tests
           command: |
-            tox -e py36,pyflakes,coverage
+            tox -e py36,pyflakes
 
       - deploy:
           name: Push coverage

tox.ini

@@ -35,7 +35,7 @@ commands =
 [testenv:coverage]
 deps = coverage
 commands =
-     {envpython} -m coverage xml
+     coverage xml
 
 [testenv:upload_coverage]
 deps = coverage