Merge pull request #4247 from lanzagar/py38-fixtest

test_txt_reader: Update test for py38 error message

Author: janezd

Orange/tests/test_txt_reader.py

@@ -89,7 +89,7 @@ def test_read_csv_with_na(self):
     def test_read_nonutf8_encoding(self):
         with self.assertRaises(ValueError) as cm:
             data = Table(test_filename('datasets/binary-blob.tab'))
-        self.assertIn('NULL byte', cm.exception.args[0])
+        self.assertIn('NUL', cm.exception.args[0])
 
         with self.assertRaises(ValueError):
             with warnings.catch_warnings():