Add key configuration option

config.yaml

@@ -3,6 +3,12 @@ options:
     type: string
     default:
     description: Package install location for Percona XtraDB Cluster (defaults to distro for >= 14.04)
+  key:
+    type: string
+    default:
+    description: |
+      Key ID to import to the apt keyring to support use with arbitary source
+      configuration from outside of Launchpad archives or PPA's.
   dataset-size:
     default: '80%'
     type: string

hooks/percona_hooks.py

@@ -81,7 +81,7 @@ def install():
             lsb_release()['DISTRIB_CODENAME'] < 'trusty':
         setup_percona_repo()
     elif config('source') is not None:
-        add_source(config('source'))
+        add_source(config('source'), config('key'))
 
     configure_mysql_root_password(config('root-password'))
     db_helper = get_db_helper()