Forked PRs are not properly detecting the circle config.yml file. For example, here is a commit that failed from a fork, yet works fine when the identical commit is pushed up to the central repository:
The failed build: https://circleci.com/gh/deviantintegral/drupal_tests/198?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link
The passed build: https://circleci.com/gh/deviantintegral/drupal_tests/200?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link
The PR: https://github.com/deviantintegral/drupal_tests/pull/42