Add a try: block to catch exceptions that occur before the main loop and to call ui.mainException().

I'm not sure if this is the "right" way to handle exceptions, but it does
correctly print the error message AFTER shutting down curses for me.

offlineimap/init.py

@@ -101,6 +101,7 @@ def startup(versionno):
 
     lock(config, ui)
 
+    try:
         if options.has_key('-l'):
             sys.stderr = ui.logfile
 
@@ -149,6 +150,9 @@ def startup(versionno):
                                        'config': config})
         t.setDaemon(1)
         t.start()
+    except:
+        ui.mainException()
+
     try:
         threadutil.exitnotifymonitorloop(threadutil.threadexited)
     except SystemExit: