Force nginx tests to run during CI
diff --git a/tests/boulder-integration.sh b/tests/boulder-integration.sh
index 08c4826768a..d86a6fb8c78 100755
--- a/tests/boulder-integration.sh
+++ b/tests/boulder-integration.sh
@@ -203,7 +203,9 @@ common revoke --cert-path "$root/conf/live/le2.wtf/cert.pem" \
 
 common unregister
 
-if type nginx;
+# Most CI systems set this variable to true.
+# If the tests are running as part of CI, Nginx should be available.
+if ${CI:-false} || type nginx;
 then
     . ./certbot-nginx/tests/boulder-integration.sh
 fi

If for some reason our Nginx set up gets broken in Travis, our tests will currently silently pass without making us aware of the issue. Let's fix this!

[Travis source](https://docs.travis-ci.com/user/environment-variables/#Default-Environment-Variables)
[Circle source](https://circleci.com/docs/1.0/environment-variables/)