Raise exception and show message to user if repo missing satellite

app/controllers/merge_requests_controller.rb

@@ -69,6 +69,8 @@ class MergeRequestsController < ProjectResourceController
       @merge_request.check_if_can_be_merged
     end
     render json: {state: @merge_request.human_state}
+  rescue Gitlab::SatelliteNotExistError
+    render json: {state: :no_satellite}
   end
   def automerge

app/views/merge_requests/show/_mr_accept.html.haml

@@ -23,6 +23,11 @@
           .clearfix
+  .automerge_widget.no_satellite{style: "display:none"}
+    .alert.alert-error
+      %span
+        %strong This repository does not have satellite. Ask administrator to fix this issue
+
   .automerge_widget.cannot_be_merged{style: "display:none"}
     .alert.alert-info
       %span

lib/gitlab/satellite/satellite.rb

 module Gitlab
+  class SatelliteNotExistError < StandardError; end
+
   module Satellite
     class Satellite
       PARKING_BRANCH = "__parking_branch"
@@ -9,8 +11,12 @@ module Gitlab
         @project = project
       end
+      def raise_no_satellite
+        raise SatelliteNotExistError.new("Satellite doesn't exist")
+      end
+
       def clear_and_update!
-        raise "Satellite doesn't exist" unless exists?
+        raise_no_satellite unless exists?
         delete_heads!
         clear_working_dir!
@@ -35,7 +41,7 @@ module Gitlab
       # * Changes the current directory to the satellite's working dir
       # * Yields
       def lock
-        raise "Satellite doesn't exist" unless exists?
+        raise_no_satellite unless exists?
         File.open(lock_file, "w+") do |f|
           f.flock(File::LOCK_EX)
@@ -55,7 +61,7 @@ module Gitlab
       end
       def repo
-        raise "Satellite doesn't exist" unless exists?
+        raise_no_satellite unless exists?
         @repo ||= Grit::Repo.new(path)
       end