Island, UT: Use count_documents instead of count

* count() is deprecated
* pytest.mark.usefixtureS

monkey/monkey_island/cc/setup/mongo/database_initializer.py

@@ -32,7 +32,7 @@ def _try_store_mitigations_on_mongo():
     mitigation_collection_name = AttackMitigations.COLLECTION_NAME
     try:
         mongo.db.validate_collection(mitigation_collection_name)
-        if mongo.db.attack_mitigations.count() == 0:
+        if mongo.db.attack_mitigations.count_documents({}) == 0:
             raise errors.OperationFailure(
                 "Mitigation collection empty. Try dropping the collection and running again"
             )

monkey/tests/unit_tests/monkey_island/cc/services/reporting/test_stolen_credentials.py

@@ -35,7 +35,7 @@ def fake_monkey():
     return monkey.id
 
 
-@pytest.mark.usefixture("uses_database")
+@pytest.mark.usefixtures("uses_database")
 def test_get_credentials(fake_monkey):
     StolenCredentials(
         identities=fake_credentials["identities"],