Prettier job failures are confusing

When Prettier fails in CI, it doesn't print a useful error message. All we get is a lousy console.log warning from eslint

Example output:

$ yarn lint
yarn run v1.13.0
$ eslint --ext .js,.vue .

/builds/gitlab-org/gitlab-ui/components/base/loading_icon/loading_icon.vue
  68:7  warning  Unexpected console statement  no-console

✖ 1 problem (0 errors, 1 warning)

Done in 7.92s.
$ yarn prettier --list-different '**/*.{js,vue}'
yarn run v1.13.0
$ /builds/gitlab-org/gitlab-ui/node_modules/.bin/prettier --list-different '**/*.{js,vue}'
components/base/form/form_select/form_select.vue
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
ERROR: Job failed: exit code 1

Better would be message saying "please run prettier --write to fix the errors"