Use SSLv23 protocol, no matter whether AUTH argument is "TLS" or "SSL". RFC-4217 states that "As the SSL/TLS protocols self-negotiate their levels, there is no need to distinguish between SSL and TLS in the application layer". Also proftpd and vsftpd behave like this so this seems to be the right way. It also seems that accepting SSLv2 is not recommended for security reasons hence accepting SSLv3 and TLSv1 only would be preferable (again, proftpd and vsftpd behave like that) but still have to figure out how to do that.
Use SSLv23 protocol, no matter whether AUTH argument is "TLS" or "SSL".
RFC-4217 states that "As the SSL/TLS protocols self-negotiate their levels, there is no need to distinguish between SSL and TLS in the application layer".
Also proftpd and vsftpd behave like this so this seems to be the right way.
It also seems that accepting SSLv2 is not recommended for security reasons hence accepting SSLv3 and TLSv1 only would be preferable (again, proftpd and vsftpd behave like that) but still have to figure out how to do that.

giampaolo/pyftpdlib