Your problem is automatically resolve when you use default inheritance of the python language.

Please see the inheritance of the python and your solution in below code.

import openerp.addons.website_crm.controllers.main as website_crm_main
class contactus_pt(website_crm_main.contactus):
    def create_lead(self, request, values, kwargs):
        """ Allow to be overrided """ 
        cr, context = request.cr, request.context 
        new_id = request.registry['crm.lead'].create(cr, SUPERUSER_ID, values, context=dict(context, mail_create_nosubscribe=True))
        request.registry['crm.lead'].message_post(cr, uid, [new_id], body=_("pasdfas"), context=context) 
        return new_id

Here according to python we have import main package from website_crm. And we have inherit contactus class inside our custom class "contactus_pt". 

This inheritance is a pure/basic python inheritance. Inside any web or website controller we can not make changes as like Odoo module. We have to use default python concept.

This is very important and less knowing things which I am going to share over here.

I am sure your issue will resolve.

Thanks.