* Relocation only implemented for Linux (requires patchelf + ldconfig -p)
* Shell-completing file name is not possible with current Pyenv completion logic:
`pyenv-complete` does not pass info about the word being completed
* Fix `save`-produced tarball to be compatible with Python-Build fetch_tarball()
* Reuse test_helper from core
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Co-authored-by: Ivan Pozdeev <vano@mail.mipt.ru>
