passenv PROCESSOR_ARCHITECTURE by default on windows (#742)

Author: asottile

changelog/740.feature.rst

@@ -0,0 +1,2 @@
+Forward ``PROCESSOR_ARCHITECTURE`` by default on Windows to fix
+``platform.machine()``.

tests/test_config.py

@@ -908,6 +908,7 @@ def test_passenv_as_multiline_list(self, tmpdir, newconfig, monkeypatch, plat):
             assert "TEMP" in envconfig.passenv
             assert "TMP" in envconfig.passenv
             assert "NUMBER_OF_PROCESSORS" in envconfig.passenv
+            assert "PROCESSOR_ARCHITECTURE" in envconfig.passenv
             assert "USERPROFILE" in envconfig.passenv
             assert "MSYSTEM" in envconfig.passenv
         else:

tox/config.py

@@ -530,6 +530,7 @@ def passenv(testenv_config, value):
             # for `multiprocessing.cpu_count()` on Windows
             # (prior to Python 3.4).
             passenv.add("NUMBER_OF_PROCESSORS")
+            passenv.add("PROCESSOR_ARCHITECTURE")  # platform.machine()
             passenv.add("USERPROFILE")  # needed for `os.path.expanduser()`
             passenv.add("MSYSTEM")  # fixes #429
         else: