Properly call error() function from ui.UIBase
Properly call error() function from ui.UIBase

Second argument is exception traceback, not the message; without this
tracebacks like mentioned in
  http://permalink.gmane.org/gmane.mail.imap.offlineimap.general/5712
were happening when this exception handling block was hit.

Signed-off-by: Eygene Ryabinkin <9f2104e8f86374257270d0eb74ac82c1c7e1ca3c@codelabs.ru>

frioux/offlineimap,frioux/offlineimap