>> FWIW, m2crypto already provides an FTP-TLS facility with an
>> ftplib-compatible API. See
http://chandlerproject.org/Projects/MeTooCrypto

Right but m2crypto is not part of the standard library (and is not going
to be anytime soon). SSL is scheduled to be in 2.6. So it would be the
natural choice to use that SSL binding to extend the ftp library. Of
course we could have a look how ftps is implemented in m2crypto.

Concerning the plain-text login. I think a FTPS class should default to
encrypted login (you could use the ftp class if you dont want). In no
way should the login credentials be sent unencrypted on default. Using
another parameter might be a soulution to that, though I would prefer
the library to raise an error if establishing an FTPS connection did not
succeed. The main program could then catch it and decide how to proceed
(using plain ftp or aborting according to a given policy).