tests: use a temporary MEDIA_ROOT (#42325)

tests/conftest.py

@@ -1,7 +1,5 @@
 import pytest
 
-from django.contrib.auth.models import User
-
 import django_webtest
 
 
@@ -11,3 +9,8 @@ def app(request):
     wtm._patch_settings()
     request.addfinalizer(wtm._unpatch_settings)
     return django_webtest.DjangoTestApp()
+
+
+@pytest.fixture(autouse=True)
+def media_root(settings, tmpdir):
+    settings.MEDIA_ROOT = str(tmpdir.mkdir('media_root'))