py3: `subprocess.py` patch needed

[o-murphy]

There are were popen and subprocess patches for py2, but we have not yes same sollution for py3 I'm not that familiar with subprocess module to make implementation based on StaSh ShThread, so help wanted.

Some packages require subprocess support, even pip require it for building wheel from sdist distribution Yes i know that compilable packages can't be installed this way, but not every sdist distributions need it.

For example pyaes is distributing as sdist only, anyway it does not use binary dependencies or compilation to build wheel, but StaSh has no possibility install it with pip cause pip uses subprocess module to process sdist distribution. So the one way was is making pyaes-whl fork that has prebuilt wheel distribution published on pypi.