Fix 'io_utils' test 'test_with_encoding_utf8'

Ref.: #120

Author: jtrh

tests/test_libs_io_utils.py

@@ -1,5 +1,6 @@
 import io
 import pathlib
+import sys
 import tempfile
 import unittest
 
@@ -69,8 +70,11 @@ def test_with_encoding_utf8(self):
 
         with tempfile.SpooledTemporaryFile(mode='rt', encoding='utf-8') as f:
             self.assertTrue(isinstance(f, tempfile.SpooledTemporaryFile))
-            # note: this is a strange case.
-            self.assertFalse(with_encoding_utf8(f))
+            if sys.version_info > (3, 7):
+                self.assertTrue(with_encoding_utf8(f))
+            else:
+                # note: this is a strange case (Python 3.7).
+                self.assertFalse(with_encoding_utf8(f))
 
         # Text mode - encoding 'latin1'