Py marker means any python not CPython (#2460)

Resolves tox-dev/tox#2566

docs/changelog/2460.bugfix.rst

@@ -0,0 +1 @@
+A ``py`` or ``python`` spec means any Python rather than ``CPython`` - by :user:`gaborbernat`.

src/virtualenv/discovery/py_spec.py

@@ -56,7 +56,7 @@ def _int_or_none(val):
                 else:
                     impl = groups["impl"]
                     if impl == "py" or impl == "python":
-                        impl = "CPython"
+                        impl = None
                     arch = _int_or_none(groups["arch"])
 
             if not ok:

tests/unit/discovery/test_py_spec.py

@@ -1,4 +1,3 @@
-import itertools
 import sys
 from copy import copy
 
@@ -46,7 +45,7 @@ def test_spec_satisfies_arch():
 
 @pytest.mark.parametrize(
     ("req", "spec"),
-    list(itertools.combinations(["py", "CPython", "python"], 2)) + [("jython", "jython")] + [("CPython", "cpython")],
+    [("py", "python"), ("jython", "jython"), ("CPython", "cpython")],
 )
 def test_spec_satisfies_implementation_ok(req, spec):
     spec_1 = PythonSpec.from_string_spec(req)
@@ -56,7 +55,7 @@ def test_spec_satisfies_implementation_ok(req, spec):
 
 
 def test_spec_satisfies_implementation_nok():
-    spec_1 = PythonSpec.from_string_spec("python")
+    spec_1 = PythonSpec.from_string_spec("cpython")
     spec_2 = PythonSpec.from_string_spec("jython")
     assert spec_2.satisfies(spec_1) is False
     assert spec_1.satisfies(spec_2) is False

tox.ini

@@ -67,7 +67,7 @@ setenv =
 skip_install = true
 deps =
     coverage>=6.5
-    diff_cover>=7.1
+    diff_cover>=7.2
 extras =
 parallel_show_output = true
 commands =
@@ -91,7 +91,7 @@ description = check that the long description is valid (need for PyPI)
 skip_install = true
 deps =
     build>=0.9
-    twine>=4.0.1
+    twine>=4.0.2
 extras =
 commands =
     python -m build -o {envtmpdir} --wheel --sdist .