yaml invalid when trying to load somthing via curl and custom header

Summary

Let's say we want to download an artifact via curl, because we do not have cross project dependencies. In this case we can do somsing like this:

curl -i -f -L -H "PRIVATE-TOKEN: ${PRIVATE_TOKEN}" -o swagger.json 'https://example.com/namespace/project/-/jobs/artifacts/develop/raw/swagger.json?job=doc'

Steps to reproduce

The .gitlab-ci.yml looks like:

pages:
  stage: deploy
  script:
    - mkdir public
    - curl -i -f -L -H "PRIVATE-TOKEN: ${PRIVATE_TOKEN}" -o swagger.json 'https://example.com/namespace/project/-/jobs/artifacts/develop/raw/swagger.json?job=doc'
    - cp swagger.json public/
  artifacts:
    paths:
     - public
  only:
   - develop

but in this case, we will get an invalid yaml error:

Status: syntax is incorrect

Error: jobs:pages:script config should be a string or an array of strings

If we remove the : from the curl header definition, the yaml parser gets happy, but the http header isn't valid any more.

Possible fixes

As workaround we can add a script that executs curl, but it isn't a nice solution.