Allow text representation of samlp.Status without XML declaration in test.

The xml.etree.ElementTree.tostring() method returns text without
XML declaration in Python 3.
This change amends test in test_12_s_utils to expect the result
with or without XML declaration.

Signed-off-by: Oleg Girko <[email protected]>

Author: OlegGirko

tests/test_12_s_utils.py

@@ -106,7 +106,7 @@ def test_status_from_tuple():
 def test_status_from_tuple_empty_message():
     stat = utils.error_status_factory((samlp.STATUS_UNKNOWN_PRINCIPAL, None))
     status_text = "%s" % stat
-    assert status_text == ERROR_STATUS_EMPTY
+    assert status_text in (ERROR_STATUS_EMPTY, ERROR_STATUS_NO_HEADER_EMPTY)
 
 
 def test_attribute_sn():