Acho que este link responde ao problema, tenho o mesmo problema no meu Sistema Linux:
This has been a long standing problem with PySVN (the Python bindings we use under the hood for SVN work).
See: http://pysvn.tigris.org/ds/viewMessage.do?dsForumId=1335&dsMessageId=2621231
Unfortunately, unless someone comes up with a solution, it looks like you'll need to configure SVN+SSH to use keys instead of passphrases.
Parece um problema conhecido que ainda não foram resolvidos.