repository/Base.py: Fix regression (UIBase is no more)

Commit e506442996 changed getglobalui() back to UIBase.getglobalui()
although the import had changed earlier, causing a regression.

Fix this by using the correct and current way of calling the ui.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

Changelog.draft.rst

@@ -19,6 +19,8 @@ Changes
 Bug Fixes
 ---------
 
+* Fix regression (UIBase is no more).
+
 
 Pending for the next major release
 ==================================

offlineimap/repository/Base.py

@@ -19,7 +19,6 @@
 from offlineimap import CustomConfig
 from offlineimap.ui import getglobalui
 import os.path
-import sys
 import traceback
 
 def LoadRepository(name, account, reqtype):
@@ -167,7 +166,7 @@ class BaseRepository(CustomConfig.ConfigHelperMixin):
                 except (KeyboardInterrupt):
                     raise
                 except:
-                    UIBase.getglobalui().warn("ERROR Attempting to make folder " \
+                    getglobalui().warn("ERROR Attempting to create folder " \
                         + key + ":"  +traceback.format_exc())
 
         #