Merge pull request #234 from nuwang/master

Pin coverage < 5

tox.ini

@@ -30,4 +30,4 @@ passenv =
     mock: CB_IMAGE_AWS CB_INSTANCE_TYPE_AWS CB_PLACEMENT_AWS AWS_ACCESS_KEY AWS_SECRET_KEY
 deps =
     -rrequirements.txt
-    coverage
+    coverage<5.0