While fixing the tkinter demos, I found some problems when moving from
mhlib to mailbox that are corrected in the attached patch.

The first fix:

-        for name, key_list in self.get_sequences():
+        for name, key_list in self.get_sequences().iteritems():

I'm not sure someone else used the module before, or at least
get_sequences() since it returns a dict and it just fails in the current
code.

The second fix is about the .mh_sequences file format I found here, it
may have some lines with one space, or two, after its content which was
causing the get_sequences() to fail too.