Docker build was fixed in PR #430, but versions >5.2.1 haven't been uploaded #544

Issue Summary

A weird bug was discovered in #426 and fixed in #430, but in the meantime builds for 4.2.1 and 4.3.0 failed. Is it possible to backport #430 to the old tags and then re-upload to Docker Hub?

Steps to Reproduce

(See the builds page.)

Technical details:

The rest of the builds were fine, but Docker was broken in builds 4.2.1 and 4.3.0. To get them up, you could:

• Merge Fix #426: Attempt to sync before executing shell command #430 into those releases and re-tag (or increment) to trigger the build. This would also send out release notifications.
• Check out those tags, manually make the change, and manually upload to Docker Hub. Probably the cleanest.

Nontechnical details:

Happy New Year!