Building Heroku-based application using gliderlabs/herokuish docker image... invalid reference format invalid reference format invalid argument "/master:72ea968afe56f32f1c83e1dcbd9c633b794209b1" for "-t, --tag" flag: invalid reference format See 'docker build --help'. Running after_script Uploading artifacts for failed job Authenticating with credentials from /root/.docker/config.json ERROR: Job failed: exit code 1