bpo-39573: Use the Py_TYPE() macro (GH-21433)

Replace obj->ob_type with Py_TYPE(obj).
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 3494f33..7bd72c9 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -1382,7 +1382,7 @@
         if (!PyLong_Check(result)) {
             PyErr_Format(PyExc_TypeError,
                          "__int__ returned non-int (type %.200s)",
-                         result->ob_type->tp_name);
+                         Py_TYPE(result)->tp_name);
             Py_DECREF(result);
             return NULL;
         }
@@ -1391,7 +1391,7 @@
                 "__int__ returned non-int (type %.200s).  "
                 "The ability to return an instance of a strict subclass of int "
                 "is deprecated, and may be removed in a future version of Python.",
-                result->ob_type->tp_name)) {
+                Py_TYPE(result)->tp_name)) {
             Py_DECREF(result);
             return NULL;
         }
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 4d511a2..87bd1ae 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -20,7 +20,7 @@
     Py_XDECREF(alias->origin);
     Py_XDECREF(alias->args);
     Py_XDECREF(alias->parameters);
-    self->ob_type->tp_free(self);
+    Py_TYPE(self)->tp_free(self);
 }
 
 static int
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 809ed85..648dd15 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -3325,7 +3325,7 @@
     }
     PyErr_Format(PyExc_TypeError,
                  "argument must be str, not %.50s",
-                 obj->ob_type->tp_name);
+                 Py_TYPE(obj)->tp_name);
     return 0;
 }
 
@@ -3361,7 +3361,7 @@
     }
     PyErr_Format(PyExc_TypeError,
                  "argument must be str or None, not %.50s",
-                 obj->ob_type->tp_name);
+                 Py_TYPE(obj)->tp_name);
     return 0;
 }