Specify Docker image for shared runners

3 jobs for master in 58 seconds (queued for 1 second)
Status Job ID Name Coverage
  Compile
passed compile #497009

00:00:30

 
  Test
passed test #497010

00:00:06

 
  Deploy
failed deploy #497011

00:00:20

 
Name Stage Failure
failed
deploy Deploy
Created fresh repository.
Checking out f103fc52 as master...

Skipping Git submodules setup
Executing "step_script" stage of the job script
/usr/bin/bash: line 103: dpl: command not found
$ dpl --provider=heroku --app=jlp19-simplewebapp --api-key=$Heroku_API_Key
Cleaning up file based variables
ERROR: Job failed: exit code 1