Get ros2.repos file using GitHub API with authentication

[christophebedard]

I tried running ros-ci-for-pr and it failed when trying to fetch the ros2.repos file:

INFO:ros_github_scripts.ci_for_pr:Creating ros2.repos Gist for PRs
Traceback (most recent call last):
  File "/home/christophe.bedard/ros-tooling/ros-github-scripts/venv/bin/ros-ci-for-pr", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/christophe.bedard/ros-tooling/ros-github-scripts/ros_github_scripts/ci_for_pr.py", line 433, in main
    gist = create_ci_gist(github_instance, chosen_pulls, parsed.target)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/christophe.bedard/ros-tooling/ros-github-scripts/ros_github_scripts/ci_for_pr.py", line 75, in create_ci_gist
    master_repos = fetch_repos(target_release)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/christophe.bedard/ros-tooling/ros-github-scripts/ros_github_scripts/ci_for_pr.py", line 65, in fetch_repos
    return toplevel_dict['repositories']
           ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
KeyError: 'repositories'

The GET request (repos_response) was returning a 404. I think this is related to the changes GitHub has been making recently to unauthenticated requests, which is what we're currently doing. Since we already have a token, we can use that to make an authenticated request. I just used the github module to fetch the file.

This also includes #25: The branch of github.com/ros2/ros2 for the Rolling distro was changed from master to rolling some time ago (like most ROS 2 repos), so no need to use master for Rolling here.

[christophebedard]

@fujitatomoya if you've started getting the above error when running ros-ci-for-pr lately (since I know you use it), this should fix it.

[clalancette]

Seems reasonable to me.

[christophebedard]

I used these changes to trigger these CI jobs: ros2/ros2_tracing#187 (comment)

[fujitatomoya]

@christophebedard i have never had this error yet, but thanks for the information. if i see those, i will upgrade the script.