Add link to buildbot results

[pitrou]

When the "test-with-buildbots" label is applied, Bedevere posts a comment to notify that builds have been scheduled, but the comment is quite unhelpful as it doesn't say how the results can be accessed.

It should be possible to add a hyperlink to the buildbot results page for the particular commit, or at least the given PR (for example https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F30617%2Fmerge or https://buildbot.python.org/all/#/changes/14341 in the case above).

[zware]

This is all handled in buildmaster-config, it just happens to be using Bedevere's credentials to post the comment.

[pablogsal]

When the "test-with-buildbots" label is applied, Bedevere posts a comment to notify that builds have been scheduled, but the comment is quite unhelpful as it doesn't say how the results can be accessed.

But I think adding a link to https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F30617%2Fmerge is a good idea that we can explore 👍