AssertionError: The container was serialized

Here is a patch to fix this error.

I applied the patch, removed the trailing spaces it introduced, and made a commit.
I did not back-port the patch to the 8.x-1.x branch, since in that branch the class doesn't implement ContainerFactoryPluginInterface.

Thank you for your report and the patch!

Automatically closed - issue fixed for 2 weeks with no activity.