From `failure` to `anyhow`

failure-to-anyhow.txt

https://github.com/filecoin-project/rust-fil-proofs/pull/956/files/4fd1396deb3172d824d97682f4366bfa9abacc09#diff-301ba6b17c22cbd0c1d0ecb79a8104be
let meta = serde_json::from_reader(file).map_err(FailureError::from)?;
->
let meta = serde_json::from_reader(file)?;


.ok_or_else(|| format_err!("could not map filename to parameter id"))?;
->
.context("could not map filename to parameter id")?;


Err(format_err!("cannot pre-commit a sector (id = {:?}) which is not fully packed (remaining space = {:?})",
->
Err(anyhow!("cannot pre-commit a sector (id = {:?}) which is not fully packed (remaining space = {:?})",


if parameter_file_path.exists() {
    rename(parameter_file_path, target_parameter_file_path)?;
    Ok(())
} else {
    Err(err_msg(ERROR_PARAMETER_FILE))
}
->
ensure!(parameter_file_path.exists(), ERROR_PARAMETER_FILE);
rename(parameter_file_path, target_parameter_file_path)?;

Ok(())


if bytes.len() != 32 {
    return Err(Error::BadFrBytes);
}
->
ensure!(bytes.len() == 32, Error::BadFrBytes);


return Err(err_msg(format!(
    "JSON file '{}' does not exist",
    &json_path.to_str().unwrap_or("")
)));
->
bail!(
    "JSON file '{}' does not exist",
    &json_path.to_str().unwrap_or("")
);


serde_json::from_reader(reader).map_err(|err| {
    failure::format_err!(
        "JSON file '{}' did not parse correctly: {}",
        &json_path.to_str().unwrap_or(""),
        err,
    )
})?
->
serde_json::from_reader(reader).with_context(|| {
    format!(
        "JSON file '{}' did not parse correctly",
        &json_path.to_str().unwrap_or(""),
    )
})?