+### Python version portability.
+
+def _iterkeys(dict): return dict.iterkeys()
+def _itervalues(dict): return dict.itervalues()
+def _iteritems(dict): return dict.iteritems()
+
+def _bin(text): return text
+def _text(bin): return bin
+
+_NUL = _bin('\0')
+_CIPHER = _bin('cipher:')
+_MAC = _bin('mac:')
+
+def _excval(): return SYS.exc_info()[1]
+
+###--------------------------------------------------------------------------