Fix implicit call to unicode() from UI functions

BaseFolder now exposes an __unicode__ method so that function needing
unicode transcoding don't crash due to ascii encoding errors.

Signed-off-by: Stéphane Albert <sheeprine@oh.its.fake.nullplace.com>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/folder/Base.py

@@ -98,6 +98,11 @@ class BaseFolder(object):
         # FIMXE: remove calls of this. We have getname().
         return self.name
 
+    def __unicode__(self):
+        # NOTE(sheeprine): Implicit call to this by UIBase deletingflags() which
+        # fails if the str is utf-8
+        return self.name.decode('utf-8')
+
     @property
     def accountname(self):
         """Account name as string"""