Rust 正确的错误处理(使用问号自动从一种错误类型转换为另一种错误类型)

我想学习如何正确处理 rust 迹中的错误.我读过book和this example；现在我想知道我应该如何处理这个函数中的错误:

fn get_synch_point(&self) -> Result<pv::synch::MeasPeriods, reqwest::Error> {
    let url = self.root.join("/term/pv/synch"); // self.root is url::Url
    let url = match url {
        Ok(url) => url,
        // ** this err here is url::ParseError and can be converted to Error::Kind https://docs.rs/reqwest/0.8.3/src/reqwest/error.rs.html#54-57 **//
        Err(err) => {
            return Err(Error {
                kind: ::std::convert::From::from(err),
                url: url.ok(),
            })
        }
    };

    Ok(reqwest::get(url)?.json()?) //this return reqwest::Error or convert to pv::sych::MeasPeriods automaticly
}      

这个代码是不正确的；它会导致编译错误:

error[E0451]: field `kind` of struct `reqwest::Error` is private
  --> src/main.rs:34:42
   |
34 |             Err(err) => return Err(Error{kind: ::std::convert::From::from(err), url: url.ok()})
   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ field `kind` is private

error[E0451]: field `url` of struct `reqwest::Error` is private
  --> src/main.rs:34:81
   |
34 |             Err(err) => return Err(Error{kind: ::std::convert::From::from(err), url: url.ok()})
   |                                                                                 ^^^^^^^^^^^^^ field `url` is private

什么是处理该案件的适当模式？对我来说，reqwest::Error在这种情况下是一个很好的解决方案，所以我希望避免定义自己的错误类型:

enum MyError {
    Request(reqwest::Error),
    Url(url::ParseError) // this already a part of request::Error::Kind!!!
}