Do not alter status_codes docstring if it is None
With PYTHONOPTIMIZE=2, the current code breaks with TypeError.
@@ -114,6 +114,7 @@ def _init():
global __doc__
__doc__ = (__doc__ + '\n' +
- '\n'.join(doc(code) for code in sorted(_codes)))
+ '\n'.join(doc(code) for code in sorted(_codes))
+ if __doc__ is not None else None)
_init()
