employee_id = self.env['hr.employee.ref'].sudo().search([('employees_id.id', '=', self.employees_id.id)])
if employee_id:
    for emp in employee_id:
        if not emp.end_date:
            action = self.env.ref('project.open_view_project_all').read()[0]
            action['domain'] = [('id', '=', emp.project_id.id)]
            # print(action['domain'])
            msg = (_('You cant add %s in this Project ,He/She is already busy with Project : %s,Please go back to the Project %s and add the End date ') % (
                    self.employees_id.name, emp.project_id.name, emp.project_id.name))
            raise RedirectWarning(msg, action['id'], _('VIEW PROJECT'), )