[1.8.x] Refs #24324 -- Fixed Python 2 test failures when path to Django source contains non-ASCII characters.

Backport of 307c0f299a from master

tests/test_runner/test_debug_sql.py

@@ -5,6 +5,7 @@ from django.db import connection
 from django.test import TestCase
 from django.test.runner import DiscoverRunner
 from django.utils import six
+from django.utils.encoding import force_text
 
 from .models import Person
 
@@ -42,8 +43,9 @@ class TestDebugSQL(unittest.TestCase):
         ).run(suite)
         runner.teardown_databases(old_config)
 
-        stream.seek(0)
-        return stream.read()
+        if six.PY2:
+            stream.buflist = [force_text(x) for x in stream.buflist]
+        return stream.getvalue()
 
     def test_output_normal(self):
         full_output = self._test_output(1)