Download uv from releases.astral.sh instead of GitHub releases (#524)

Since Astral now mirror uv releases to `releases.astral.sh`, which
is backed by Cloudflare R2 / CDN, and so is more reliable than
GitHub releases.

See:
astral-sh/uv#18207 (comment)

GUS-W-21561072.

Author: edmorley

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Updated uv from 0.10.7 to 0.10.9. ([#523](https://github.com/heroku/buildpacks-python/pull/523))
+- Switched to downloading uv from `releases.astral.sh` instead of GitHub releases. ([#524](https://github.com/heroku/buildpacks-python/pull/524))
 
 ## [6.0.1] - 2026-03-03
 

src/errors.rs

@@ -516,15 +516,15 @@ fn on_uv_layer_error(error: UvLayerError) {
             DownloadUnpackArchiveError::Request(ureq_error) => log_error(
                 "Unable to download uv",
                 formatdoc! {"
-                    An error occurred while downloading uv from GitHub.
+                    An error occurred while downloading uv from Astral's website.
                     
                     In some cases, this happens due to a temporary issue with
-                    the network connection or GitHub's API/CDN.
+                    the network connection or Astral's CDN, Cloudflare.
 
                     Try building again to see if the error resolves itself.
 
-                    If that doesn't help, check the status of GitHub here:
-                    https://www.githubstatus.com
+                    If that doesn't help, check the status of Cloudflare here:
+                    https://www.cloudflarestatus.com
                     
                     Details: {ureq_error}
                 "},

src/layers/uv.rs

@@ -87,7 +87,7 @@ pub(crate) fn install_uv(
             // 1. It's currently slower than the glibc variant: https://github.com/astral-sh/uv/issues/10610
             // 2. At the moment this buildpack only supports Ubuntu anyway (we only compile Python runtimes for Ubuntu).
             let archive_url = format!(
-                "https://github.com/astral-sh/uv/releases/download/{UV_VERSION}/uv-{ARCH}-unknown-linux-gnu.tar.gz"
+                "https://releases.astral.sh/github/uv/releases/download/{UV_VERSION}/uv-{ARCH}-unknown-linux-gnu.tar.gz"
             );
             let layer_bin_dir = layer.path().join("bin");
             utils::download_and_unpack_nested_gzip_archive(&archive_url, &layer_bin_dir, 1)