Deprecated Symfony constraint 'min' option

The test in question has

    $context_definition = ContextDefinition::create('text')
      ->setLabel('Test text area')
      ->setDescription('Enter text, minimum 40 characters.')
      ->addConstraint('Length', ['min' => 40]);

I will investigate adding the "allowEmptyString" option.

I tried adding
->addConstraint('Length', ['min' => 40, 'allowEmptyString' => FALSE]).

At core 8.8 and 8.9 this gives the error
Symfony\Component\Validator\Exception\InvalidOptionsException: The options "allowEmptyString" do not exist in constraint "Drupal\Core\Validation\Plugin\Validation\Constraint\LengthConstraint". in Symfony\Component\Validator\Constraint->__construct()
This was using Symfony 3.4.

Running tests at core 9.0 work fine, there is no deprecation warning, and they all pass. This was using symfony 4.4

I also found #3117863: [Symfony 5] Using the "Symfony\Component\Validator\Constraints\Length" constraint with the "min" option without setting the "allowEmptyString" one is deprecated which dealt with the problem in Core 9.0 and 9.1

This can be fixed, but first to demonstrate the existing behavior here's a patch which adds drupalci.yml with suppress-deprecations: false

That was a bit tedious, but I finally got the right job config for core 9.0 (php7.3 MySql 5.7), and we can see that there are 59 passes and 1 failure, as expected.

Here is a patch which uses the version_compare(\Drupal::VERSION, '9.0', '>=') to make the necessary distinction. I know that these types of hack are not ideal, but it will allow the tests at 9.0 to run without deprecated warnings.

That's nice, we have green at 8.8 and 9.0.

I confirm that this also runs with zero deprecation on the Travis builds at core 9.0

So here is the actual patch for review and commit, without the temporary addition of drupalci.yml