How can I override the HTTP methods for PUT and DELETE in a Flask Module?

I am having a hard time trying to modify the Flask request object before routing occurs.

My API Module (not my entire Flask app) depends on faking PUT and DELETE operations by sending a special header. I need to check out the contents of the "-Method" header and modify the Flask Request object accordingly, before Flask does its routing.

This is the short, pythonic, explicit code I'd like to work:

@api.before_request
def method_scrubbing():
    if request.headers.has_key('-Method'):
        method = request.headers['-Method'].upper()
        tagalog.log("in before_request, -Method = {}".format(method), 'force')
        if method not in ['PUT', 'DELETE']:
            raise ApiMethodException(method)
        else:
            request.method = method

...but I get a "read only property" error from werkzeug: http://drktd.com/74yk

I've seem Armin's post at http://flask.pocoo.org/snippets/38/ but this appears to be app-wide (not specific to a module).