DEV: Raise exceptions when jobs fail in test mode

Previously jobs would fail silently in test mode. Now they will raise the exception and cause the relevant test to fail. This identified a few broken tests, which I will fix in a followup commit

lib/discourse.rb

@@ -54,6 +54,8 @@ module Discourse
       current_db: cm.current_db,
       current_hostname: cm.current_hostname
     }.merge(context))
+
+    raise ex if Rails.env.test?
   end
 
   # Expected less matches than what we got in a find