unify Windows and non-Windows "make quicktest"

[zooko]

8e2506675355ddaf improved "make quicktest" on non-Windows and left the old code in place on Windows (by branching on if sys.platform == "win32"). While I appreciate the fact that Brian wanted to avoid changing behavior that he wasn't going to test, I think it is important to have as few if sys.platform == "win32" in the code as possible, so I intend to test this behavior on Windows and hopefully just remove the if.

[warner]

(fixed minor typo in description)

Sounds good to me.

[davidsarah]

os.execve has different behaviour on Windows; it doesn't replace the current process. So you at least need a sys.exit(0) after os.execve.

[davidsarah]

Actually I'm mistaken; although there is no direct equivalent to exec on Windows, os.execve does exit automatically, so it's close enough.

[davidsarah]

This was fixed in 2a51a7bb900d512f.

(On the ticket1306 branch, make quicktest no longer uses misc/build_helpers/run-with-pythonpath.py in any case, and neither does anything else. I'll open a new ticket to remove it.)

[davidsarah]

Actually for the use in make quicktest and make quicktest-coverage, it was incorrect to make the change in 2a51a7bb900d512f (I was wrong about that in comment:4), because it would have caused the make command to exit leaving the test running. Probably no-one noticed because they don't use the Makefile on Windows, since it requires gmake.

Anyway, [4927/ticket1306] fixes that, because bin\tahoe.pyscript doesn't use os.execve. The optimization that was made in 8e2506675355ddaf is applicable to bin/tahoe, but it would have to fall back to subprocess.call on Windows. (This optimization should not be made in 1.8.2 since it is a potentially destabilizing change. I'd rather get rid of the extra subprocess completely on all platforms by munging sys.path instead of setting PYTHONPATH.)