#[error(transparent)]
    Io(#[from] std::io::Error),

    #[error("{context} ({source})")]
    Io { source: std::io::Error, context: String },

        let canon_path = match Path::new(pat).canonicalize() {

        let path = Path::new(pat);
        let canon_path = match path.canonicalize() {

            Err(e) => return Err(e.into()),

            Err(source) => {
                let e = Error::Io {
                    source,
                    context: format!("error canonicalizing path {}", path.display()),
                };
                return Err(e);
            },

    #[error(transparent)]
    Io(#[from] std::io::Error),

    #[error("{context} ({source})")]
    Io { source: std::io::Error, context: String },

    #[error(transparent)]
    Io(#[from] std::io::Error),

    #[error("{context} ({source})")]
    Io { source: std::io::Error, context: String },

            Err(e) => return Err(E::from(Error::from(e))),

            Err(source) => {
                let e = Error::Io {
                    source,
                    context: format!("unable to create temp file in {}", self.changes_dir.display())
                };
                return Err(e.into());
            },

        if let Err(e) = std::fs::create_dir_all(file_name.parent().unwrap()) {
            return Err(E::from(Error::from(e)));

        let dir = file_name.parent().unwrap();
        if let Err(source) = std::fs::create_dir_all(dir) {
            let e = Error::Io {
                source,
                context: format!("unable to create directory {}", dir.display()),
            };
            return Err(e.into());