[1.6.x] Fix #21185: Added tests for unescape_entities.

Also fixed a py3 incompatibility.
Thanks to brutasse for the report.

Backport of 3754f4ad41 from master.

tests/utils_tests/test_text.py

@@ -106,3 +106,16 @@ class TestUtilsText(SimpleTestCase):
         )
         for value, output in items:
             self.assertEqual(text.slugify(value), output)
+
+    def test_unescape_entities(self):
+        items = [
+            ('', ''),
+            ('foo', 'foo'),
+            ('&', '&'),
+            ('&', '&'),
+            ('&', '&'),
+            ('foo & bar', 'foo & bar'),
+            ('foo & bar', 'foo & bar'),
+        ]
+        for value, output in items:
+            self.assertEqual(text.unescape_entities(value), output)