unicode: Changed handling of None in smart_unicode/force_unicode. There is no

case when converting it to a unicode string seems useful, so keep it as None.
Fixed #4435.


git-svn-id: http://code.djangoproject.com/svn/django/branches/unicode@5388 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/utils/encoding.py

@@ -27,6 +27,8 @@ def force_unicode(s, encoding='utf-8', errors='strict'):
     Similar to smart_unicode, except that lazy instances are resolved to
     strings, rather than kept as lazy objects.
     """
+    if s is None:
+        return s
     if not isinstance(s, basestring,):
         if hasattr(s, '__unicode__'):
             s = unicode(s)
@@ -72,5 +74,7 @@ def iri_to_uri(iri):
     # The list of safe characters here is constructed from the printable ASCII
     # characters that are not explicitly excluded by the list at the end of
     # section 3.1 of RFC 3987.
+    if iri is None:
+        return iri
     return urllib.quote(smart_str(iri), safe='/#%[]=:;$&()+,!?')