Check this answer on StackOverflow
https://stackoverflow.com/questions/51342512/user-deprecated-doctrine-common-classloader-is-deprecated

This was fixed in Doctrine ORM (see doctrine/orm#7326) but not released yet. I am closing here as there is nothing we can do in Symfony.

Thanks a lot, guys! )))

I was able to remove this warning by strictly requiring: "doctrine/common": "2.8.1" for now.

Hmm, I have 2.9.0 and still can see this deprecation in the profiler...

@crabnky As suggested by @ragboyjr, I have set "doctrine/common": "2.8.1", and not ^2.9 and the deprecation is now fixed.

@crabnky this deprecation is precisely triggered when you have doctrine/common 2.9.0 (because the 2.9.0 release is the one adding the warnings, and the fix in the ORM is not released)

Oh, thanks, understood. Do you know when the new version is planned to be released?

no. That's something you need to ask to the Doctrine ORM maintainers.