Close #390: Ignore !buildbot comment if no builder matches

[vstinner]

Also, match the regex anywhere in the builder name, not only at the start.

[vstinner]

Ok, the change works as expected: python/cpython#109698 (comment)

I just made a typo, fixed by: 69e9ee1

[sentry]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️NameError: name 'builder' is not definedcustom.pr_testing in <listcomp>View Issue

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[vstinner]

‼️ NameError: name 'builder' is not defined custom.pr_testing in View Issue

I fixed it.