fix travis

.travis.yml

@@ -1,11 +1,10 @@
 language: python
-dist: trusty
 sudo: required
-group: edge
 python:
   - "3.6"
 env:
   - DJANGO_VERSION=2.0
+  global:
     - CC_TEST_REPORTER_ID=6c015c866a94cfb5b7a046e9a0725a6a02224b1023eeef9ea2db63426beb3fd3
 install:
   - pip install Django==$DJANGO_VERSION
@@ -18,7 +17,7 @@ before_script:
   - ./cc-test-reporter before-build
 script:
   - tox
-  - coverage run runtests.py --source="pwa" -v 2
+  - coverage run runtests.py --source=pwa -v 2
 after_script:
   - coverage xml
   - if [[ "$TRAVIS_PULL_REQUEST" == "false" && "$TRAVIS_PYTHON_VERSION" == "3.6" ]]; then ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT; fi