error_chain!{
errors {
InvalidChildElement(child: String, parent: &'static str) {
description("invalid child element")
display("invalid child element '{}' in {}", child, String::from(*parent))
}
InvalidElementLacksAttribute(attr: &'static str) {
description("invalid element, lacks required attribute")
display("invalid element, lacks required attribute {}", String::from(*attr))
}
}
}