Allow test suite to run out-of-tree ... such as in .pybuild/python_X.Y/build.
This involves including on extra package in the installation but is mostly bodging things to substitute `$PYBUILD_TEST_BASE_OVERRIDE` for `$PWD` when hunting for test resources.
Compatibility with `argparse-manpage` * Refactor construction of `argparse.ArgumentParser` into a `get_argparser()` function in each binary. * Set `prog` property (the default uses `sys.arg[0]` which breaks with `argparse-manpage`, arguably this is an `argparse-manpage` bug). * Set the `man_short_description` property based on the first line of the description. This is used as a summary in the `NAME` section of the man page.
