restrict test on allowDiskUse to mongoDB >= 4.4 in CI + ran black

tests/utils.py

@@ -1,3 +1,4 @@
+import operator
 import unittest
 
 import pytest
@@ -33,6 +34,10 @@ def get_as_pymongo(doc):
     return doc.__class__.objects.as_pymongo().get(id=doc.id)
 
 
+def requires_mongodb_gte_44(func):
+    return _decorated_with_ver_requirement(func, (4, 4), oper=operator.ge)
+
+
 def _decorated_with_ver_requirement(func, mongo_version_req, oper):
     """Return a MongoDB version requirement decorator.