dev-python/cython: Improve py39 patch to avoid breaking py27

Signed-off-by: Michał Górny <mgorny@gentoo.org>

dev-python/cython/files/cython-0.29.20-py39-classmeth.patch

@@ -1,59 +1,34 @@
-From 1bb26b964060392ecb08c3b6c8ca4626e5c1eec7 Mon Sep 17 00:00:00 2001
-From: Jeroen Demeyer <jeroen.k.demeyer@gmail.com>
-Date: Wed, 28 Aug 2019 10:56:28 +0200
-Subject: [PATCH] Always bind Cython functions
+From c29a7818d3b6806a457af698aec446d3d28d4f80 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Micha=C5=82=20G=C3=B3rny?= <mgorny@gentoo.org>
+Date: Sun, 14 Jun 2020 13:45:21 +0200
+Subject: [PATCH] Always bind Cython functions in py3
 
+Rebased for cython 0.29.x, and made conditional to Python 3.  This
+does not solve the original staticmethod problem in Python 2 but it does
+resolve classmethod problems in Python 3.9.  Therefore, it unbreaks
+other packages on Python 3.9, improves overall state for Python 3
+and does not introduce regressions in Python 2.
 ---
- Cython/Utility/CythonFunction.c | 15 ---------------
- tests/run/cyfunction.pyx        | 12 ++++++++++++
- 2 files changed, 12 insertions(+), 15 deletions(-)
+ Cython/Utility/CythonFunction.c | 2 ++
+ 1 file changed, 2 insertions(+)
 
 diff --git a/Cython/Utility/CythonFunction.c b/Cython/Utility/CythonFunction.c
-index 01ff1e0dd4..0758548cb3 100644
+index a65c8eee36..33d0a4750a 100644
 --- a/Cython/Utility/CythonFunction.c
 +++ b/Cython/Utility/CythonFunction.c
-@@ -552,21 +552,6 @@ static int __Pyx_CyFunction_traverse(__pyx_CyFunctionObject *m, visitproc visit,
+@@ -548,6 +548,7 @@ static int __Pyx_CyFunction_traverse(__pyx_CyFunctionObject *m, visitproc visit,
  
  static PyObject *__Pyx_CyFunction_descr_get(PyObject *func, PyObject *obj, PyObject *type)
  {
--    __pyx_CyFunctionObject *m = (__pyx_CyFunctionObject *) func;
--
--    if (m->flags & __Pyx_CYFUNCTION_STATICMETHOD) {
--        Py_INCREF(func);
--        return func;
--    }
--
--    if (m->flags & __Pyx_CYFUNCTION_CLASSMETHOD) {
--        if (type == NULL)
--            type = (PyObject *)(Py_TYPE(obj));
--        return __Pyx_PyMethod_New(func, type, (PyObject *)(Py_TYPE(type)));
--    }
--
--    if (obj == Py_None)
--        obj = NULL;
++#if PY_MAJOR_VERSION < 3
+     __pyx_CyFunctionObject *m = (__pyx_CyFunctionObject *) func;
+ 
+     if (m->flags & __Pyx_CYFUNCTION_STATICMETHOD) {
+@@ -563,6 +564,7 @@ static PyObject *__Pyx_CyFunction_descr_get(PyObject *func, PyObject *obj, PyObj
+ 
+     if (obj == Py_None)
+         obj = NULL;
++#endif
      return __Pyx_PyMethod_New(func, obj, type);
  }
  
-diff --git a/tests/run/cyfunction.pyx b/tests/run/cyfunction.pyx
-index cbce48bcfc..bbd2cefb83 100644
---- a/tests/run/cyfunction.pyx
-+++ b/tests/run/cyfunction.pyx
-@@ -376,6 +376,18 @@ class TestUnboundMethod:
-     def meth(self): pass
- 
- 
-+class TestStaticmethod(object):
-+    """
-+    >>> x = TestStaticmethod()
-+    >>> x.staticmeth(42)
-+    42
-+    >>> x.staticmeth.__get__(42)()
-+    42
-+    """
-+    @staticmethod
-+    def staticmeth(arg): return arg
-+
-+
- cdef class TestOptimisedBuiltinMethod:
-     """
-     >>> obj = TestOptimisedBuiltinMethod()