[py3] Ported django.utils.encoding.

* Renamed smart_unicode to smart_text (but kept the old name under
  Python 2 for backwards compatibility).
* Renamed smart_str to smart_bytes.
* Re-introduced smart_str as an alias for smart_text under Python 3
  and smart_bytes under Python 2 (which is backwards compatible).
  Thus smart_str always returns a str objects.
* Used the new smart_str in a few places where both Python 2 and 3
  want a str.

django/db/models/options.py

@@ -8,7 +8,7 @@ from django.db.models.fields import AutoField, FieldDoesNotExist
 from django.db.models.fields.proxy import OrderWrt
 from django.db.models.loading import get_models, app_cache_ready
 from django.utils.translation import activate, deactivate_all, get_language, string_concat
-from django.utils.encoding import force_unicode, smart_str
+from django.utils.encoding import force_text, smart_bytes
 from django.utils.datastructures import SortedDict
 from django.utils import six
 
@@ -199,7 +199,7 @@ class Options(object):
         return '<Options for %s>' % self.object_name
 
     def __str__(self):
-        return "%s.%s" % (smart_str(self.app_label), smart_str(self.module_name))
+        return "%s.%s" % (smart_bytes(self.app_label), smart_bytes(self.module_name))
 
     def verbose_name_raw(self):
         """
@@ -209,7 +209,7 @@ class Options(object):
         """
         lang = get_language()
         deactivate_all()
-        raw = force_unicode(self.verbose_name)
+        raw = force_text(self.verbose_name)
         activate(lang)
         return raw
     verbose_name_raw = property(verbose_name_raw)