Add retry when the creation of a Pull Request fails

[Justinzobel]

Recently KDE Gear 23.08.1 was released and about 80 of the packages got PRs which are nice and easy to merge.

However, the remaining 50ish got a branch but no Merge Request. I checked the f-e-d-c logs and I can see 71 instances of this error as GitHub is rate-limiting the API.

github.GithubException.GithubException: 403 {'message': 'You have exceeded a secondary rate limit and have been temporarily blocked from content creation. Please retry your request again later. If you reach out to GitHub Support for help, please include the request ID 9F80:72AD:4EA5F9:A00E26:6502EE6B.', 'documentation_url': '<a href="https://docs.github.com/rest/overview/resources-in-the-rest-api#secondary-rate-limits">https://docs.github.com/rest/overview/resources-in-the-rest-api#secondary-rate-limits</a>'}

I did a quick look and it's using urllib3 which has a retry function (https://urllib3.readthedocs.io/en/stable/reference/urllib3.util.html)

It even has a backoff_factor variable which can increase the time between retries and RETRY_AFTER_STATUS_CODES which could be set to 403 which is the error code GitHub is sending back when you hit the rate limit.

From the link to the GitHub REST API docs above it mentions:

You should wait and try your request at a later time. If the retry-after response header is present, you should not retry your request until after that many seconds has elapsed. If the x-ratelimit-remaining header is 0, you should not retry your request until after the time, in UTC epoch seconds, specified by the x-ratelimit-reset header. Otherwise, wait for an exponentially increasing amount of time between retries, and throw an error after a specific number of retries.

This indicates that respect_retry_after_header in urllib3 would also be an effective way of ensuring the next attempt succeeds.