global: use python3 in shebangs Python 3 is the future. We want Python scripts to be using Python 3 by default. This change updates all `#!/usr/bin/env python` shebangs to use `python3`. Does this mean all scripts use or require Python 3: no. In the test environment, the `PATH` environment variable in tests is updated to guarantee that the Python executable used to run run-tests.py is used. Since test scripts all now use `#!/usr/bin/env python3`, we had to update this code to install a `python3` symlink instead of `python`. It is possible there are some random scripts now executed with the incorrect Python interpreter in some contexts. However, I would argue that this was a pre-existing bug: we should almost always be executing new Python processes using the `sys.executable` from the originating Python script, as `python` or `python3` won't guarantee we'll use the same interpreter. Differential Revision: https://phab.mercurial-scm.org/D9273

#!/usr/bin/env python3

from __future__ import absolute_import

import os
import sys

os.chdir(os.getenv('TESTTMP'))

if sys.argv[1] != "user@dummy":
    sys.exit(-1)

os.environ["SSH_CLIENT"] = "%s 1 2" % os.environ.get('LOCALIP', '127.0.0.1')

log = open("dummylog", "ab")
log.write(b"Got arguments")
for i, arg in enumerate(sys.argv[1:]):
    log.write(b" %d:%s" % (i + 1, arg.encode('latin1')))
log.write(b"\n")
log.close()
hgcmd = sys.argv[2]
if os.name == 'nt':
    # hack to make simple unix single quote quoting work on windows
    hgcmd = hgcmd.replace("'", '"')
r = os.system(hgcmd)
sys.exit(bool(r))