run-tests: work around the Windows firewall popup for server processes Windows doesn't have a `python3` executable, so cc0b332ab9fc attempted to work around the issue by copying the current python to `python3.exe`. That put it in `_tmpbindir` because of failures in `test-run-tests.t` when using `_bindir`, which looked like a process was trying to open it to write out a copy while it was in use. (Interestingly, I couldn't reproduce this running the test by itself in a loop for a couple of hours, but it happens constantly when running all tests.) The problem with using `_tmpbindir` is that it is the randomly generated path for the test run, and instead of Windows Firewall remembering the executable signature or image hash when allowing the process to open a server port, it apparently remembers the image path. That means every run will trigger a popup to allow it, which is bad for firing off a test run and walking away. I tried to symlink to the python executable, but that currently requires admin priviledges[1]. This will prompt the first time if the underlying python binary has never opened a server port, but appears to avoid it on subsequent runs. [1] https://bugs.python.org/issue40687 Differential Revision: https://phab.mercurial-scm.org/D9815