def add_pgp_key(self, public_key, signature, guid):
        gpg = gnupg.GPG()
        gpg.import_keys(public_key)
        if gpg.verify(signature) and guid in signature:
            p = self.profile.PublicKey()
            p.public_key = public_key
            p.signature = signature
            self.profile.pgp_key.MergeFrom(p)
            self.db.profile.set_proto(self.profile.SerializeToString())
            return True
        else:
            return False
Adds a pgp public key to the profile. The user must have submitted a
dataset/ETHPy150Open OpenBazaar/OpenBazaar-Server/market/profile.py/Profile.add_pgp_key