Commits adding CHANGES entries and/or release notes do not need a commit
log message. Do not warn about a missing commit log message for such
commits to make the warning more meaningful.
Certain rules of the BIND development process are not codified anywhere
and/or are used inconsistently. In an attempt to improve this
situation, add a GitLab CI job which uses Danger Python to add comments
to merge requests when certain expectations are not met. Two categories
of feedback are used, only one of which - fail() - causes the GitLab CI
job to fail. Exclude dangerfile.py from Python QA checks as the way the
contents of that file are evaluated triggers a lot of Flake8 and PyLint
warnings.
