Py3: Replace six.moves imports

Replace six.moves and six.StringIO/BytesIO imports with cannonical
Python 3 packages.

Note: six.moves.input behaves differently than builtin input function.
Therefore I left six.moves.input for now.

See: https://pagure.io/freeipa/issue/7715
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>

ipalib/parameters.py

@@ -103,11 +103,9 @@ import re
 import decimal
 import base64
 import datetime
+from xmlrpc.client import MAXINT, MININT
 
 import six
-# pylint: disable=import-error
-from six.moves.xmlrpc_client import MAXINT, MININT
-# pylint: enable=import-error
 from cryptography import x509 as crypto_x509
 
 from ipalib.text import _ as ugettext