Make tests again compatible with Python 3.8

Author: fangerer

graalpython/com.oracle.graal.python.test/src/tests/cpyext/__init__.py

@@ -149,6 +149,12 @@ def file_not_empty(path):
 #include <Python.h>
 {defines}
 
+#if !GRAALVM_PYTHON && (PY_VERSION_HEX < 0x03090000)
+#define Py_SET_REFCNT(ob, v) ((_PyObject_CAST(ob)->ob_refcnt = (v)))
+#define Py_SET_TYPE(ob, v)   ((_PyObject_CAST(ob)->ob_type) = (v))
+#define Py_SET_SIZE(ob, v)   ((_PyVarObject_CAST(ob)->ob_size = (Py_ssize_t) (v)))
+#endif
+
 {customcode}
 
 static PyObject* test_{capifunction}(PyObject* module, PyObject* args) {{
@@ -466,6 +472,12 @@ def CPyExtType(name, code, **kwargs):
     template = """
     #include "Python.h"
 
+    #if !GRAALVM_PYTHON && (PY_VERSION_HEX < 0x03090000)
+    #define Py_SET_REFCNT(ob, v) ((_PyObject_CAST(ob)->ob_refcnt = (v)))
+    #define Py_SET_TYPE(ob, v)   ((_PyObject_CAST(ob)->ob_type) = (v))
+    #define Py_SET_SIZE(ob, v)   ((_PyVarObject_CAST(ob)->ob_size = (Py_ssize_t) (v)))
+    #endif
+
     {includes}
 
     typedef struct {{