django - TypeError: %o format: a number is required, not unicode -

def _force_i18n(self, i):     test = '{% load i18n %}{% language {} %}'.format(self.language)     userlanguage = test + + '{% endlanguage %}'      return userlanguage 

here, self.language return either u'en' or u'fr'. i've got following error

traceback (most recent call last):   file "/home/jeremie/projects/work_projects/24-django/loanwolf/messaging/utils.py", line 170, in render     return template(self._force_i18n(content)).render(context(context))   file "/home/jeremie/projects/work_projects/24-django/loanwolf/messaging/utils.py", line 126, in _force_i18n     test = '{% load i18n %}{% language {} %}'.format(self.language) typeerror: %o format: number required, not unicode 

how fix it?