I rechecked #23351 and in msg249924 Donald did disclaim any guarantee that using main() would work forever.  He suggested instead using subprocess and the command line interface as presumably more stable.

In tem_pip_v3.py Upendra switched to using subprocess and I presume he stuck with that in spite of any suggestion otherwise from me.  If the pip command line interface is changed, *every* program that uses it could be broken.

I agree with Ned that pip_gui should ideally be part of the pip package, I would be happy if Donald were to review what Upendra has and will produce, pronounce it good, and ask to have it for pip.