When ever I try to confirm a Sales Order, I get the error below. I am not sure what it's referring to at all. Has anyone seen this error before and what did you do to fix it?

Traceback (most recent call last): File "/opt/odoo/odoo-server/openerp/http.py", line 525, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/opt/odoo/odoo-server/openerp/http.py", line 562, in dispatch result = self._call_function(**self.params) File "/opt/odoo/odoo-server/openerp/http.py", line 302, in _call_function return checked_call(self.db, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/service/model.py", line 113, in wrapper return f(dbname, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/http.py", line 299, in checked_call return self.endpoint(*a, **kw) File "/opt/odoo/odoo-server/openerp/http.py", line 791, in __call__ return self.method(*args, **kw) File "/opt/odoo/odoo-server/openerp/http.py", line 395, in response_wrap response = f(*args, **kw) File "/opt/odoo/odoo-server/addons/web/controllers/main.py", line 953, in call_button action = self._call_kw(model, method, args, {}) File "/opt/odoo/odoo-server/addons/web/controllers/main.py", line 941, in _call_kw return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper return old_api(self, *args, **kwargs) File "/opt/odoo/.local/share/Odoo/addons/8.0/sale_dummy_confirmation/sale.py", line 30, in action_button_confirm res = super(sale_order, self).action_button_confirm(cr, uid, ids, context=context) File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper return old_api(self, *args, **kwargs) File "/opt/odoo/odoo-server/addons/portal_sale/portal_sale.py", line 67, in action_button_confirm return super(sale_order, self).action_button_confirm(cr, uid, ids, context=context) File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper return old_api(self, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/api.py", line 393, in old_api result = new_api(recs, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/api.py", line 397, in new_api result = [method(rec, *args, **kwargs) for rec in self] File "/opt/odoo/.local/share/Odoo/addons/8.0/calendar_service/models/sale.py", line 40, in action_button_confirm return super(sale_order, self).action_button_confirm() File "/opt/odoo/odoo-server/openerp/api.py", line 239, in wrapper return new_api(self, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/api.py", line 546, in new_api result = method(self._model, cr, uid, self.ids, *args, **kwargs) File "/opt/odoo/odoo-server/addons/sale/sale.py", line 598, in action_button_confirm self.signal_workflow(cr, uid, ids, 'order_confirm') File "/opt/odoo/odoo-server/openerp/api.py", line 241, in wrapper return old_api(self, *args, **kwargs) File "/opt/odoo/odoo-server/openerp/models.py", line 3491, in signal_workflow result[res_id] = workflow.trg_validate(uid, self._name, res_id, signal, cr) File "/opt/odoo/odoo-server/openerp/workflow/__init__.py", line 85, in trg_validate return WorkflowService.new(cr, uid, res_type, res_id).validate(signal) File "/opt/odoo/odoo-server/openerp/workflow/service.py", line 91, in validate res2 = wi.validate(signal) File "/opt/odoo/odoo-server/openerp/workflow/instance.py", line 75, in validate wi.process(signal=signal, force_running=force_running, stack=stack) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 120, in process ok = self._split_test(activity['split_mode'], signal, stack) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 248, in _split_test self._join_test(t[0], t[1], stack) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 257, in _join_test WorkflowItem.create(self.session, self.record, activity, inst_id, stack=stack) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 95, in create workflow_item.process(stack=stack) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 116, in process if not self._execute(activity, stack): File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 162, in _execute returned_action = self.wkf_expr_execute(activity) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 313, in wkf_expr_execute return self.wkf_expr_eval_expr(activity['action']) File "/opt/odoo/odoo-server/openerp/workflow/workitem.py", line 291, in wkf_expr_eval_expr result = eval(line, env, nocopy=True) File "/opt/odoo/odoo-server/openerp/tools/safe_eval.py", line 313, in safe_eval return eval(c, globals_dict, locals_dict) File "", line 1, in <module> ValueError: "name 'check_validity' is not defined" while evaluating u'check_validity()'