try to get the build working again

Author: dcrosta

.travis.yml

@@ -6,9 +6,9 @@ python:
   - 3.4
   - 3.5
   - 3.6
-  - 3.7-dev
+  # - 3.7-dev
 services: mongodb
 install: pip install -r test-requirements.txt -e .
 script: py.test --tb=native tests
 before_script:
-  - mongo test_db --eval 'db.addUser("flask", "pymongo");'
+  - mongo test_db --eval 'db.createUser({user:"flask", pwd:"pymongo", roles:["readWrite"]})