Try enabling builds for stretch and bionic.

rpki-pbuilder.sh

@@ -12,7 +12,8 @@ python rpki-pbuilder.py					\
     --git-tree $HOME/source.ng/rpki.net/		\
     --apt-tree $HOME/repository.ng/			\
     --url-path /APTng					\
-    --releases debian/jessie ubuntu/xenial
+    --releases debian/jessie  ubuntu/xenial		\
+	       debian/stretch ubuntu/bionic
 
 python rpki-pbuilder.py					\
     --git-tree $HOME/source.ng/rpki.net/		\