py3: allow run-tests.py to run on Windows This is now functional: HGMODULEPOLICY=py py -3 run-tests.py --local test-help.t --pure --view bcompare However, on this machine without a C compiler, it tries to load cext anyway, and blows up. I haven't looked into why, other than to see that it does set the environment variable. When the test exits though, I see it can't find killdaemons.py, get-with-headers.py, etc. I have no idea why these changes are needed, given that it runs on Linux. But os.system() is insisting that it take a str, and subprocess.Popen() blows up without str: Errored test-help.t: Traceback (most recent call last): File "run-tests.py", line 810, in run self.runTest() File "run-tests.py", line 858, in runTest ret, out = self._run(env) File "run-tests.py", line 1268, in _run exitcode, output = self._runcommand(cmd, env) File "run-tests.py", line 1141, in _runcommand env=env) File "C:\Program Files\Python37\lib\subprocess.py", line 756, in __init__ restore_signals, start_new_session) File "C:\Program Files\Python37\lib\subprocess.py", line 1100, in _execute_child args = list2cmdline(args) File "C:\Program Files\Python37\lib\subprocess.py", line 511, in list2cmdline needquote = (" " in arg) or ("\t" in arg) or not arg TypeError: argument of type 'int' is not iterable This is exactly how it crashes when trying to spin up a pager too. I left one instance of os.system() unchanged in _installhg(), because it doesn't get there.