On Python 3.2, calling abort() on an ftplib.FTP object will cause an exception:

>>> ftp = ftplib.FTP('localhost')
>>> ftp.abort()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.2/ftplib.py", line 246, in abort
    self.sock.sendall(line, MSG_OOB)
TypeError: 'str' does not support the buffer interface

The offending line, ftplib.py:246, should be replaced by
self.sock.sendall(line.encode(self.encoding), MSG_OOB)

Thanks for the report.  If you would like to turn your suggestion into a diff file (see guidelines at http://docs.python.org/devguide) containing the code change and a test, you could get into the Misc/ACKS file and get eternal glory :)

This is a nasty one and mainly it's the reason why there are no tests for abort() method.
In FTP, ABOR command is supposed to be sent as OOB (out-of-band) "urgent" data and the dummy FTP server we're using for the funcional tests must handle this appopriately.

In practical terms this means that when the client calls self.sock.sendall(line, MSG_OOB) the server is supposed to call socket.recv(1024, MSG_OOB).
Since our server uses asyncore this becomes quite twisted to handle.
This can be avoided by setting SO_OOBINLINE which tells the server to handle the urgent data inline meaning that both plain and urgent data can be received with a normal sock.recv(1024) call.

The patch in attachment does this and also fixes FTP_TLS.abort() which is not able to accept the extra MSG_OOB flag argument.

There's a side note: on certain platforms SO_OOBINLINE has no effect, resulting in asyncore's handle_expt method being called, see:
http://code.google.com/p/pyftpdlib/source/browse/trunk/pyftpdlib/ftpserver.py#2064
I haven't handled this case in my patch because I'm not sure what platforms are broken.
I'd say we can commit this patch as-is, wait for the buildbots to turn red and then disable the test for those platforms afterwards.

New changeset 31220cd936d2 by Giampaolo Rodola' in branch '3.1':
#12002 - ftplib's abort() method raises TypeError
http://hg.python.org/cpython/rev/31220cd936d2