- #37798 had to be reverted because a new flakyness appeared ([see
  CI build](https://buildkite.com/rails/rails/builds/65467#efaa1dd5-aaf4-43a1-a204-d1c42abf614d))

  This failure isn't related to the change itself.
  If you apply this diff, the test will some time to time fail.
  Even without my changes.

  ```diff
  diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index b5c1cac3d9..09fe0ddd7f 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -1127,7 +1127,6 @@ def test_no_automatic_savepoint_for_inner_transaction
   end
 end if Topic.connection.supports_savepoints?

-if ActiveRecord::Base.connection.supports_transaction_isolation?
   class ConcurrentTransactionTest < TransactionTest
     # This will cause transactions to overlap and fail unless they are performed on
     # separate database connections.
@@ -1198,4 +1197,3 @@ def test_transaction_isolation__read_committed
       assert_equal original_salary, Developer.find(1).salary
     end
   end
-end
  ```

  SQlite3 isn't safe to run in a multi threaded environment unless
  sqlite is compiled with a special flag which isn't our case.
  Ref https://www.sqlite.org/threadsafe.html