Correct usage

setuptools/tests/__init__.py

@@ -18,7 +18,7 @@ from setuptools.depends import Require
 
 c_type = os.environ.get("LC_CTYPE", os.environ.get("LC_ALL"))
 is_ascii = c_type in ("C", "POSIX")
-fail_on_ascii = pytest.mark.xfail(is_ascii, "Test fails in this locale")
+fail_on_ascii = pytest.mark.xfail(is_ascii, reason="Test fails in this locale")
 
 def makeSetup(**args):
     """Return distribution from 'setup(**args)', without executing commands"""