AbstractController::DoubleRenderError at /gitlab-org/gitlab-test/merge_requests/8/approvers/1Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like "redirect_to(...) and return".
AbstractController::DoubleRenderError - Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like "redirect_to(...) and return".: actionpack (4.2.8) lib/action_controller/metal/redirecting.rb:72:in `redirect_to' actionpack (4.2.8) lib/action_controller/metal/flash.rb:57:in `redirect_to' actionpack (4.2.8) lib/action_controller/metal/instrumentation.rb:64:in `block in redirect_to' activesupport (4.2.8) lib/active_support/notifications.rb:164:in `block in instrument' activesupport (4.2.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (4.2.8) lib/active_support/notifications.rb:164:in `instrument' actionpack (4.2.8) lib/action_controller/metal/instrumentation.rb:63:in `redirect_to' app/controllers/application_controller.rb:52:in `redirect_back_or_default' app/controllers/projects/approvers_controller.rb:12:in `destroy' actionpack (4.2.8) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (4.2.8) lib/abstract_controller/base.rb:198:in `process_action' actionpack (4.2.8) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (4.2.8) lib/abstract_controller/callbacks.rb:20:in `block in process_action' activesupport (4.2.8) lib/active_support/callbacks.rb:117:in `call' activesupport (4.2.8) lib/active_support/callbacks.rb:555:in `block (2 levels) in compile' activesupport (4.2.8) lib/active_support/callbacks.rb:505:in `call' activesupport (4.2.8) lib/active_support/callbacks.rb:498:in `block (2 levels) in around' activesupport (4.2.8) lib/active_support/callbacks.rb:313:in `block (2 levels) in halting' lib/gitlab/i18n.rb:39:in `with_locale' lib/gitlab/i18n.rb:45:in `with_user_locale'
What's odd is that in the dev environment, it seems that we make a call to the /merge_requests/<iid>/approvers/<id> endpoint, which results in that error but does remove the approver. However, I don't see this happen on 9.3.2.
@stanhu I wasn't on GitLab EE, but looking at that code, I think it happens when you're not authorised to do the action, as authorize_* will redirect (which is a pretty bad bug, as it will still remove the approver!).
However, you are authorised - you have master access on that group, so I'm not sure how that part happened, and the approver was not removed in your gif.