This prevents STDOUT lines from appearing out of order relative to
STDERR lines in the test log, which makes it much easier to understand
what's happening.
Devel::Autoflush is from https://metacpan.org/pod/Devel::Autoflush and
is licensed under the terms of the Apache 2.0 license.
The version of Test::More available in CentOS/RHEL 6 doesn't include
`subtest`, which we want to use. We can revert this commit once we
drop support for CentOS/RHEL 6.
The code is licensed under the same terms as Perl 5 itself:
https://github.com/Test-More/test-more/blob/v1.302175/LICENSE
