let tests fail in CI if a snapshot doesn't exist

Author: daniel-wer

.circleci/config.yml

@@ -10,6 +10,8 @@ jobs:
       USER_UID: 1001
       USER_GID: 1001
       TZ: Europe/Berlin
+      # This will be picked up by ava so that the tests fail if a snapshot doesn't exist during CI, see https://github.com/avajs/ava/issues/1585
+      CI: 1
     steps:
       - checkout
       - run: