ctypes: fix undefine variable PY3

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@68369 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/python/ctypes/ctypesgencore/parser/lex.py

@@ -34,6 +34,7 @@ try:
 except ImportError:
     # python2
     bytes = str
+    PY3 = False
 
 
 import operator