aggregate coverage metrics of unit tests across packages (#115)

aggregate coverage metrics of unit tests across packages
diff --git a/openstack/common/extensions/testing/doc.go b/openstack/common/extensions/testing/doc.go
index 7603f83..24b0795 100644
--- a/openstack/common/extensions/testing/doc.go
+++ b/openstack/common/extensions/testing/doc.go
@@ -1 +1,2 @@
+// common_extensions
 package testing