AO3-4728 Error message for subscribing to deleted item (#4910) #2

Job	Run time
rake db:otwseed	1m 13s
rspec spec/controllers	11m 14s
rspec spec/models	5m 32s
rspec --exclude-pattern 'spec/{controllers,models}/*/.rb'	7m 18s
cucumber features/admins	5m 51s
cucumber features/bookmarks	4m 51s
cucumber features/collections	5m 56s
cucumber features/comments_and_kudos	6m 23s
cucumber features/gift_exchanges	6m 20s
cucumber features/importing	2m 56s
cucumber features/other_a	10m 21s
cucumber features/other_b	6m 16s
cucumber features/prompt_memes_a	4m 29s
cucumber features/prompt_memes_b	3m 58s
cucumber features/prompt_memes_c	4m 44s
cucumber features/search	7m 17s
cucumber features/tag_sets	3m 36s
cucumber features/tags_and_wrangling	5m 59s
cucumber features/users	4m 48s
cucumber features/works	13m 11s
	2h 2m 13s

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