Add programmatic support for rerunning the current program inside a venv

Python programs often need to be run inside a venv in order to allow the use of packages from pypi.org. But creating and entering a venv before running a script is a barrier, especially if a python program has been written for use by people who are not particularly familiar with python. So what i’d like is a new function in the standard venvmodule called something like venv.enter(), typically to be called at the start of execution. It would do nothing if we are already in a venv, otherwise it w...