Case with strange bug with monolog and validation

There is MyEntity with UniqueEntity constraint set for uniqueField. One entity is created and stored in DB, the new one created and ValidatorInterface->validate() is called.
It should return validation error for UniqueEntity constraint but it does not. Why? Because there is monolog handler MyHandler registered and it has ValidatorInterface injected.
That's it. Handler does not do anything by it self. Removing handler registration from config/packages/monolog.yaml or removing ValidatorInterface injection from MyHandler fixes the problem and validator works as expected.
This project is setup with sqlite but the same problem happens with mysql.

Setup project

git clone git@github.com:aurelijusrozenas/validator-monolog-bug.git
cd validator-monolog-bug
composer install
bin/console doctrine:migrations:migrate -n

Run command to see the problem

bin/console app

You should see either Validation failed because it did not detect failing constraint. or Everything is working correctly.. To change behaviour change config/packages/monolog.yaml or src/Monolog/MyHandler.php (search for FIXME).