Added rescue to retry the pdf thumbnail on error 3 times. refs #923
Added rescue to retry the pdf thumbnail on error 3 times. refs #923

jeremyf/sufia,samvera/hyrax,zhang4952/scholarsphere,zhang4952/scholarsphere,zhang4952/scholarsphere,ndlib/scholarsphere,samvera/hyrax,samvera/hyrax,zhang4952/scholarsphere,samvera/hyrax,ndlib/scholarsphere,jeremyf/sufia,ndlib/scholarsphere