bug: fix replacement for param writer_name -> writer correctly. Use the html4css1 writer for now. If you use the html5_polyglot you end up with: <main> processed rst </main> rather than (html4css1 writer's): <div class="document"> processed rst </div> there can only be one <main> per document. Each message must not be inside a <main> tag. I could string munge the main tag to a div. But that's ugly. The correct way is to subclass html5_polyglot and override the HTMLTrnslator::documenttag_args replacing {'tagname': 'main'} with {'tagname': 'div', "CLASS": "document"} or something similar. That's a change for another time.

def audit_html_files(db, cl, nodeid, newvalues):
    if 'type' in newvalues and newvalues['type'] == 'text/html':
        newvalues['type'] = 'text/plain'
    

def init(db):
    db.file.audit('set', audit_html_files)
    db.file.audit('create', audit_html_files)