clean up some duplicate code in Errdesc
clean up some duplicate code in Errdesc

Reviewed By: jeremydubreil

Differential Revision: D2670354

fb-gh-sync-id: d5e664f

kstreee/infer,jvillard/infer,kstreee/infer,ropas/infer,blzq/infer,jsachs/infer,blzq/infer,ropas/infer,jvillard/infer,xennygrimmato/infer,jvillard/infer,kageiit/infer,jsachs/infer,facebook/infer,facebook/infer,facebook/infer,kstreee/infer,jsachs/infer,facebook/infer,ropas/infer,ryoon/infer,kageiit/infer,jvillard/infer,kageiit/infer,blzq/infer,blzq/infer,jvillard/infer,kstreee/infer,jvillard/infer,kageiit/infer,facebook/infer,jsachs/infer,jsachs/infer,ryoon/infer,xennygrimmato/infer,blzq/infer,kstreee/infer,xennygrimmato/infer,ryoon/infer,kageiit/infer,ryoon/infer,xennygrimmato/infer,ryoon/infer,ropas/infer,ropas/infer,kageiit/infer,blzq/infer,xennygrimmato/infer,facebook/infer,jvillard/infer,xennygrimmato/infer,kageiit/infer,xennygrimmato/infer,facebook/infer,jsachs/infer,kstreee/infer,ropas/infer,ryoon/infer