JSON strings are not allowed to contain control characters (characters in
the range U+0000 through U+001F). However, simplejson will raise no
exception when these characters are included in a string.

>>> simplejson.loads (u'["A\u001FZ"]')
[u'A\x1fZ']

This means that users of simplejson must check the string manually to
ensure it has no invalid characters contained in it.