It is trivial to fix this, however there's a compatibility issue I'm
concerned about: the key constructed using the fixed code looks
different than the key constructed by the old, buggy code. This means
that if you have written data to a file encrypted with the old rotor
module, you won't be able to decrypt it using the new module.
For me personally this isn't a problem, but I can imagine that there
are others who have used this extensively. If this is the case for
you, please speak up! We may provide a backward compatibility hack
for you (basically you can use <<19, or live with the compiler
warnings...). If I don't hear from anyone, I'll just fix it and
release the next version with an incompatible rotor module.
--Guido van Rossum, CWI, Amsterdam <Guido.van.Rossum@cwi.nl>