Changed import order

These changes close the lintian warning C0411.

offlineimap/repository/__init__.py

@@ -14,8 +14,8 @@
 #    along with this program; if not, write to the Free Software
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 
-import six
 from sys import exc_info
+import six
 
 try:
     from configparser import NoSectionError