symfony fixtures cannot delete or update a parent row

* you can add to problem entity field, which is described in error onDelete="set null"

* or deny to purge your database, add to your command key --append.

Unable to find mapping information for the class Context

Need to fully configure sonata-classification-bundle, its needed for modern versions of sonata-media.

admin_sonata_classification_context_create" as such route does not exist in SonataAdminBundle:Core:add_block.html.twig

just cache:clear and cache:clear -e prod