Add guard around pgp_key migration
Add guard around pgp_key migration

The production db has the field, but doesn't have the migration
recorded, so we ignore a duplicate run.

technomancy/clojars-web,nberger/clojars-web,technomancy/clojars-web,ato/clojars-web,clojars/clojars-web,tobias/clojars-web,ato/clojars-web,nberger/clojars-web,tobias/clojars-web,tobias/clojars-web,clojars/clojars-web,clojars/clojars-web