PLAIN fails with long password

[progval]

Session log:

1450737977.917 1: connects to server.
1450737977.917 1 -> S: CAP LS 302
1450737977.917 1 -> S: NICK registration_user
1450737977.917 1 -> S: USER r e g :user
1450737977.917 1 -> S: CAP END
[…]
1450737977.959 S -> 1: :MyLittleServer 376 registration_user :End of /MOTD command.
1450737977.959 S -> 1: :MyLittleServer PONG synchronize264323.757849863
1450737977.959 1 -> S: REG CREATE foo passphrase barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar
1450737977.959 1 -> S: PING synchronize264323.796269205
1450737978.306 S -> 1: :MyLittleServer 920 registration_user foo :Account created
1450737978.343 S -> 1: :MyLittleServer 900 registration_user registration_user!~r@localhost foo :You are now logged in as foo
1450737978.343 S -> 1: :MyLittleServer 903 registration_user :Authentication successful
1450737978.343 S -> 1: :MyLittleServer PONG synchronize264323.796269205
1450737978.344 1 -> S: PING synchronize264324.180339827
1450737978.344 S -> 1: :MyLittleServer PONG synchronize264324.180339827
1450737978.344 1: disconnects from server.
1450737978.344 1: connects to server.
1450737978.344 1 -> S: CAP LS 302
1450737978.346 S -> 1: :MyLittleServer CAP * LS * :away-notify account-notify echo-message userhost-in-names metadata-notify server-time cap-notify extended-join sasl=PLAIN
1450737978.346 S -> 1: :MyLittleServer CAP * LS account-tag
1450737978.346 1 -> S: AUTHENTICATE PLAIN
1450737978.346 S -> 1: :MyLittleServer NOTICE * :*** Looking up your hostname...
1450737978.383 S -> 1: :MyLittleServer NOTICE * :*** Checking Ident
1450737978.383 S -> 1: :MyLittleServer NOTICE * :*** Found your hostname: localhost
1450737978.383 S -> 1: :MyLittleServer NOTICE * :*** No Ident response
1450737978.384 S -> 1: :MyLittleServer AUTHENTICATE +
1450737978.384 1 -> S: AUTHENTICATE Zm9vAGZvbwBiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJiYXJi
1450737978.384 1 -> S: AUTHENTICATE YXJiYXJiYXI=
1450737978.731 S -> 1: :MyLittleServer 904 * :SASL authentication failed
1450737978.733 1: disconnects from server.

[DanielOaks]

Yeah, we don't handle the 400-character-limit of SASL that well yet. I can fix this.

[progval]

If you are looking for an implementation: https://github.com/ProgVal/Limnoria/blob/15d59d1153ae5648533ccaae91c4af70ba901cc8/src/ircutils.py#L874-L901
And test cases: https://github.com/ProgVal/Limnoria/blob/15d59d1153ae5648533ccaae91c4af70ba901cc8/test/test_ircutils.py#L394-L425