The existing Python 3.4.10 archive actually contained Python 3.7.2,
since the version in the source URL was not updated when the file was
created in #813.
The build formula now uses the shared build script approach like all of
the other build scripts, which ensures the version can never get out of
sync (since it's extracted from the formula filename).
The build for Heroku-18 failed to compile `_ssl` properly (even though
the build exited zero) since Python 3.4.10 is old enough it doesn't work
well with libssl1.1. Installing `libssl1.0-dev` in the build image
locally resolved the issue - however we don't want to use that in the
future for newer Python, so I've not updated the `heroku-18.Dockerfile`.
In addition, with the rebuilt archives the tests now pass on Cedar-14,
so no longer need to be marked as failing.
Closes @W-7947035@.
Ed Morley