diff --git a/tests/modeltests/invalid_models/tests.py b/tests/modeltests/invalid_models/tests.py
index 9d7adb045c..e1fc68743e 100644
--- a/tests/modeltests/invalid_models/tests.py
+++ b/tests/modeltests/invalid_models/tests.py
@@ -1,11 +1,11 @@
 import copy
 import sys
-from io import BytesIO
 
 from django.core.management.validation import get_validation_errors
 from django.db.models.loading import cache, load_app
 
 from django.utils import unittest
+from django.utils.six import StringIO
 
 
 class InvalidModelTestCase(unittest.TestCase):
@@ -16,7 +16,7 @@ class InvalidModelTestCase(unittest.TestCase):
         # coloring attached (makes matching the results easier). We restore
         # sys.stderr afterwards.
         self.old_stdout = sys.stdout
-        self.stdout = BytesIO()
+        self.stdout = StringIO()
         sys.stdout = self.stdout
 
         # This test adds dummy applications to the app cache. These
diff --git a/tests/regressiontests/fixtures_regress/tests.py b/tests/regressiontests/fixtures_regress/tests.py
index ab93341699..41be31ccd7 100644
--- a/tests/regressiontests/fixtures_regress/tests.py
+++ b/tests/regressiontests/fixtures_regress/tests.py
@@ -4,7 +4,6 @@ from __future__ import absolute_import, unicode_literals
 
 import os
 import re
-from io import BytesIO
 
 from django.core import management
 from django.core.management.base import CommandError
@@ -14,6 +13,7 @@ from django.db.models import signals
 from django.test import (TestCase, TransactionTestCase, skipIfDBFeature,
     skipUnlessDBFeature)
 from django.test.utils import override_settings
+from django.utils.six import StringIO
 
 from .models import (Animal, Stuff, Absolute, Parent, Child, Article, Widget,
     Store, Person, Book, NKChild, RefToNKChild, Circle1, Circle2, Circle3,
@@ -276,7 +276,7 @@ class TestFixtures(TestCase):
         )
         animal.save()
 
-        stdout = BytesIO()
+        stdout = StringIO()
         management.call_command(
             'dumpdata',
             'fixtures_regress.animal',
@@ -305,7 +305,7 @@ class TestFixtures(TestCase):
         """
         Regression for #11428 - Proxy models aren't included when you dumpdata
         """
-        stdout = BytesIO()
+        stdout = StringIO()
         # Create an instance of the concrete class
         widget = Widget.objects.create(name='grommet')
         management.call_command(
@@ -380,7 +380,7 @@ class TestFixtures(TestCase):
             )
 
     def test_loaddata_not_existant_fixture_file(self):
-        stdout_output = BytesIO()
+        stdout_output = StringIO()
         management.call_command(
             'loaddata',
             'this_fixture_doesnt_exist',
@@ -465,7 +465,7 @@ class NaturalKeyFixtureTests(TestCase):
             commit=False
             )
 
-        stdout = BytesIO()
+        stdout = StringIO()
         management.call_command(
             'dumpdata',
             'fixtures_regress.book',
diff --git a/tests/regressiontests/m2m_through_regress/tests.py b/tests/regressiontests/m2m_through_regress/tests.py
index 73a13654e7..458c194f89 100644
--- a/tests/regressiontests/m2m_through_regress/tests.py
+++ b/tests/regressiontests/m2m_through_regress/tests.py
@@ -1,10 +1,9 @@
 from __future__ import absolute_import
 
-from io import BytesIO
-
 from django.core import management
 from django.contrib.auth.models import User
 from django.test import TestCase
+from django.utils.six import StringIO
 
 from .models import (Person, Group, Membership, UserMembership, Car, Driver,
     CarDriver)
@@ -70,11 +69,11 @@ class M2MThroughTestCase(TestCase):
 
         pks = {"p_pk": p.pk, "g_pk": g.pk, "m_pk": m.pk}
 
-        out = BytesIO()
+        out = StringIO()
         management.call_command("dumpdata", "m2m_through_regress", format="json", stdout=out)
         self.assertEqual(out.getvalue().strip(), """[{"pk": %(m_pk)s, "model": "m2m_through_regress.membership", "fields": {"person": %(p_pk)s, "price": 100, "group": %(g_pk)s}}, {"pk": %(p_pk)s, "model": "m2m_through_regress.person", "fields": {"name": "Bob"}}, {"pk": %(g_pk)s, "model": "m2m_through_regress.group", "fields": {"name": "Roll"}}]""" % pks)
 
-        out = BytesIO()
+        out = StringIO()
         management.call_command("dumpdata", "m2m_through_regress", format="xml",
             indent=2, stdout=out)
         self.assertEqual(out.getvalue().strip(), """
@@ -142,6 +141,6 @@ class ThroughLoadDataTestCase(TestCase):
 
     def test_sequence_creation(self):
         "Check that sequences on an m2m_through are created for the through model, not a phantom auto-generated m2m table. Refs #11107"
-        out = BytesIO()
+        out = StringIO()
         management.call_command("dumpdata", "m2m_through_regress", format="json", stdout=out)
         self.assertEqual(out.getvalue().strip(), """[{"pk": 1, "model": "m2m_through_regress.usermembership", "fields": {"price": 100, "group": 1, "user": 1}}, {"pk": 1, "model": "m2m_through_regress.person", "fields": {"name": "Guido"}}, {"pk": 1, "model": "m2m_through_regress.group", "fields": {"name": "Python Core Group"}}]""")
diff --git a/tests/regressiontests/staticfiles_tests/tests.py b/tests/regressiontests/staticfiles_tests/tests.py
index 19951f100b..d68f211535 100644
--- a/tests/regressiontests/staticfiles_tests/tests.py
+++ b/tests/regressiontests/staticfiles_tests/tests.py
@@ -7,7 +7,6 @@ import posixpath
 import shutil
 import sys
 import tempfile
-from io import BytesIO
 
 from django.template import loader, Context
 from django.conf import settings
@@ -194,7 +193,7 @@ class TestFindStatic(CollectionTestCase, TestDefaults):
     Test ``findstatic`` management command.
     """
     def _get_file(self, filepath):
-        out = BytesIO()
+        out = six.StringIO()
         call_command('findstatic', filepath, all=False, verbosity=0, stdout=out)
         out.seek(0)
         lines = [l.strip() for l in out.readlines()]
@@ -206,7 +205,7 @@ class TestFindStatic(CollectionTestCase, TestDefaults):
         """
         Test that findstatic returns all candidate files if run without --first.
         """
-        out = BytesIO()
+        out = six.StringIO()
         call_command('findstatic', 'test/file.txt', verbosity=0, stdout=out)
         out.seek(0)
         lines = [l.strip() for l in out.readlines()]