Required to build binaries that link against Python.
Carl Meyer, the champion for PEP 0405, has confirmed that there isn't a particular reason why `venv` doesn't do that.

* Adjust tests: update Pip URLs, update expected output to match newer code
* Test library: improve failure message to eliminate the illusion of extra leading space in "actual" output
* Use Bats 1.2.0 like Pyenv
* Install greadlink for old MacOS
* Delete duplicate test

find proper source version from pyenv if the given executable is only
basename or is a shim script.

https://www.python.org/dev/peps/pep-0370/

It will be done by `get-pip.py` and we don't have to do anything explicitly.

Install script of setuptools-6.1/pip-1.5.6 will create those links if needed

While this could work in general, it fails in the end, because
whitespace is not allowed/supported in the shebang line with the
scripts in the created virtualenv.