locale.strxfrm throws error 22 when passed category is not

[oussjarrousse]

I am now getting an error related to the use of locale.strxfrm in 516 in journal.py.

Traceback (most recent call last):
  File "/Users/ouss/Documents/workspace/rednotebook/rednotebook/journal.py", line 624, in <module>
    main()
  File "/Users/ouss/Documents/workspace/rednotebook/rednotebook/journal.py", line 606, in main
    journal = Journal()
  File "/Users/ouss/Documents/workspace/rednotebook/rednotebook/journal.py", line 238, in __init__
    self.open_journal(journal_path)
  File "/Users/ouss/Documents/workspace/rednotebook/rednotebook/journal.py", line 401, in open_journal
    self.frame.categories_tree_view.categories = self.categories
  File "/Users/ouss/Documents/workspace/rednotebook/rednotebook/journal.py", line 514, in categories
    return sorted(
OSError: [Errno 22] Invalid argument

This happens when the category is in the en_US.UTF-8 locale... for example Arabic characters...

[oussjarrousse]

duplicate of #778