For functions which return a PyObject* but use "null" for the
reference count field, state that the return value is always NULL.

(Useful for some PyErr_*() flavors.)
diff --git a/Doc/tools/anno-api.py b/Doc/tools/anno-api.py
index 33f85fb..eddb3eb 100755
--- a/Doc/tools/anno-api.py
+++ b/Doc/tools/anno-api.py
@@ -49,7 +49,11 @@
                     sys.stderr.write("No refcount data for %s\n" % s)
                 else:
                     if info.result_type == "PyObject*":
-                        rc = info.result_refs and "New" or "Borrowed"
+                        if info.result_refs is None:
+                            rc = "Always \NULL{}"
+                        else:
+                            rc = info.result_refs and "New" or "Borrowed"
+                            rc = rc + " reference"
                         line = r"\begin{cfuncdesc}[%s]{PyObject*}{" % rc \
                                + line[prefix_len:]
             output.write(line)