Sadly, the granularity of the DRF doesn't allow to override just a method to deal with etags. I can inherit from the original mixin but the only method will be overridden so I think it's useless.

The support of etags in DRF is discussed in [this issue](https://github.com/tomchristie/django-rest-framework/issues/32) (and a PR [rejected by the maintainer](https://github.com/tomchristie/django-rest-framework/pull/773))