run-tests: deal with distutil deprecation
PEP 632 recommend the use of `packaging.version` to replace the deprecated
`distutil.version`. So lets do it.
Set up
$ hg init repo
$ cd repo
Try to import an empty patch
$ hg import --no-commit - <<EOF
> EOF
applying patch from stdin
abort: stdin: no diffs found
[10]
No dirstate backups are left behind
$ ls .hg/dirstate* | sort
.hg/dirstate