Wrong import of i18n content

[miceno]

I have a dataset on utf-8, containing Spanish tilde chars. Here it is:

ESPAÑA
    MADRID
FRANCIA
    PARÍS

When trying to import with import_categories, it fails.

(pytesting)orestes-retina:core_categories$ python manage.py import_categories --settings=settings.development core_categories/fixtures/bug-categories-utf8.txt 
Traceback (most recent call last):
  File "manage.py", line 16, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/django/core/management/__init__.py", line 399, in execute_from_command_line
    utility.execute()
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/django/core/management/base.py", line 242, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/django/core/management/base.py", line 285, in execute
    output = self.handle(*args, **options)
  File "/Users/orestes/Downloads/devel/bullipedia-core/core_categories/categories/management/commands/import_categories.py", line 90, in handle
    self.parse_lines(data)
  File "/Users/orestes/Downloads/devel/bullipedia-core/core_categories/categories/management/commands/import_categories.py", line 73, in parse_lines
    current_parents = {0: self.make_category(line)}
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/django/db/transaction.py", line 431, in inner
    return func(*args, **kwargs)
  File "/Users/orestes/Downloads/devel/bullipedia-core/core_categories/categories/management/commands/import_categories.py", line 37, in make_category
    slug=slugify(SLUG_TRANSLITERATOR(string.strip()))[:49],
  File "/Users/orestes/Downloads/pytesting/lib/python2.7/site-packages/slugify.py", line 26, in slugify
    unicodedata.normalize('NFKD', string)
TypeError: must be unicode, not str

Googling about the error I found a reference to slugify expecting a unicode string.