These issues are addressed in our latest change of shifting to Contenthandler (https://gerrit.wikimedia.org/r/295670 ). The same is pulled in http://newsletter-test.wmflabs.org/ and I can see that the error reported is fixed neatly there.
I just checked the same on the master branch too, and it seems fixed there too.
Alright. Thank you. I would love this to be tested in master too, as I merged the contenthandler changesets yesterday. Once that change go deep, we might've to even drop all the existing newsletters.