[3.7] bpo-34725: Adds _Py_SetProgramFullPath so embedders may override sys.executable (GH-9860)

[zooba]

https://bugs.python.org/issue34725

[serhiy-storchaka]

Why _Py_SetProgramFullPathand not Py_SetProgramFullPath?

[zooba]

Because if someone uses it in 3.7.2, their code won't be compatible with 3.7.1 and earlier, so it shouldn't be a public API. (The use I have planned is internal, but requires the API to be exposed.)

[serhiy-storchaka]

Have you planned to use it in CPython or in a tied third-party project?

[zooba]

CPython. It's needed for https://bugs.python.org/issue34977, and there's no reason to delay that until 3.8 since it isn't a new platform.