hghave: fix the definition of `python3` to work on Windows
Both py2 and py3 executables are named `python.exe`, and may or may not be on
PATH. So use the dispatcher executable that comes with py3 to fetch the version
of the latest py3 executable. This allows at least one relnotes test to run on
Windows.
Differential Revision: https://phab.mercurial-scm.org/D10694
from __future__ import absolute_import
import hashlib
try:
from ..thirdparty import sha1dc # pytype: disable=import-error
sha1 = sha1dc.sha1
except (ImportError, AttributeError):
sha1 = hashlib.sha1