message: Return error on 404
diff: @@ -1250,6 +1250,7 @@ async fn install_webc_package_inner(url: &Url, checksum: &str) -> Result<(), any
  .header(ACCEPT, "application/webc")
  .send()
  .await
  + .and_then(|response| response.error_for_status())
  .map_err(|e| anyhow::anyhow!("{e}"))
  .context(anyhow::anyhow!("install_webc_package: failed to GET {url}"))?;
  