Hello friends, it was solve this way:

def onchange_partner_id(self, cr, uid, ids, part=False, context=None):
    #res = super(project_project, self).onchange_partner_id(self, cr, uid, ids, part, context)
    '''The part and context parameters was removed'''
    res = super(project_project, self).onchange_partner_id(self, cr, uid, ids)

Thank you all!

Your function must be:

res = super(project_project, self).onchange_partner_id(self, cr, uid, ids, part, context):

Hello! I am assuming you have something like:

def onchange_partner_id(self, cr, uid, ids, part, context=None):
    if context is None:
        context = {}
    res = super(project_project, self).onchange_partner_id(cr, uid, ids, part, context=context)
    ...
    return res

If this is so, probably the problem is in the .xml. In the field where you put the on_change=onchange_partner_id(...), probably you have some other argument besides partner_id (assuming that this is the name of the field that you want to use), maybe context?. It should only be:

 on_change=onchange_partner_id(partner_id)

Hope this helps you!