Follow up forand
Whilst we have _entity_form for our defaults in routing, it can't be expected to deal with entity add callbacks, as these need to create a psuedo entity first and the keys they need to set vary (eg menu items may need a plid) or are dynamic (eg node/add/type and block/add/custom_block_type).
This leaves the controller methods for callbacks like block/add/custom_block_typeneeding to call entity_get_form from their controllers which breaks our OO goal.
This issue tracks moving entity_get_form to Drupal\Core\Entity\EntityManager::getForm()
PASSED: [[SimpleTest]]: [MySQL] 58,092 pass(es).
FAILED: [[SimpleTest]]: [MySQL] Failed to run tests: PHP Fatal error encountered during run_tests.sh. See review log for details..
FAILED: [[SimpleTest]]: [MySQL] Setup environment: Test cancelled by admin prior to completion.