Backport PR #5866: Make test robust against differences in line endings

git on Windows can change line endings on checkout, which was leading to a test failure.
Backport PR #5869: Catch more errors from clipboard access on Windows
Backport PR #5871: specify encoding in msgpack.unpackb

otherwise, it will leave strings as utf8 bytes, causing test failures on Python 3.
backport backport_pr.py from master
update gh_api and github_stats for 2.1


- pull requests are marked with milestones
- get pull request authors for backports
What’s new for 2.1