Display error depending on current locale

[tonioo]

KeyError: u'pl_PL'
  File "django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "django/utils/decorators.py", line 185, in inner
    return func(*args, **kwargs)
  File "django/utils/decorators.py", line 185, in inner
    return func(*args, **kwargs)
  File "django/contrib/auth/decorators.py", line 23, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "modoboa/admin/lib.py", line 43, in wrapped_f
    return f(request, *args, **kwargs)
  File "modoboa_webmail/views.py", line 625, in index
    response = globals()[action](request)
  File "modoboa_webmail/views.py", line 410, in listmailbox
    }, request
  File "django/template/loader.py", line 68, in render_to_string
    return template.render(context, request)
  File "django/template/backends/django.py", line 66, in render
    return self.template.render(context)
  File "django/template/base.py", line 207, in render
    return self._render(context)
  File "django/template/base.py", line 199, in _render
    return self.nodelist.render(context)
  File "django/template/base.py", line 990, in render
    bit = node.render_annotated(context)
  File "django/template/base.py", line 957, in render_annotated
    return self.render(context)
  File "django/template/defaulttags.py", line 216, in render
    nodelist.append(node.render_annotated(context))
  File "django/template/base.py", line 957, in render_annotated
    return self.render(context)
  File "django/template/base.py", line 1040, in render
    output = self.filter_expression.resolve(context)
  File "django/template/base.py", line 736, in resolve
    new_obj = func(obj, *arg_vals)
  File "modoboa_webmail/templatetags/webmail_tags.py", line 284, in parse_imap_header
    value = getattr(imapheader, "parse_%s" % header)(value)
  File "modoboa_webmail/lib/imapheader.py", line 119, in parse_date
    return date_format(ndate, DATETIME_FORMATS[current_language]['LONG'])