Python 3 preparation: convert print to a function. Tool-assisted patch. It is possible that some "from __future__ import print_function" are not in fact needed, if a file only uses print() with a single string as an argument and so would work fine in Python 2 without that import.

def audit_html_files(db, cl, nodeid, newvalues):
    if newvalues.has_key('type') 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)