execute test asset download as part of snippet build

crates/build/re_dev_tools/src/build_examples/snippets.rs

@@ -36,8 +36,11 @@ impl Snippets {
         let snippet_root = snippets_dir.join("all");
         let snippets = collect_snippets_recursively(&snippet_root, &config, &snippet_root)?;
 
-        println!("Running {} snippets…", snippets.len());
+        println!("Download test assets…");
         let progress = MultiProgress::new();
+        download_test_assets(&progress)?;
+
+        println!("Running {} snippets…", snippets.len());
         let results: Vec<anyhow::Result<PathBuf>> = snippets
             .into_par_iter()
             .map(|example| example.build(&progress, &self.output_dir))
@@ -190,3 +193,12 @@ struct OptOut {
     /// example name -> languages
     run: HashMap<String, Vec<String>>,
 }
+
+fn download_test_assets(progress: &MultiProgress) -> anyhow::Result<()> {
+    let download_script = re_build_tools::cargo_metadata()?
+        .workspace_root
+        .join("tests/assets/download_test_assets.py");
+    let mut cmd = Command::new("python3");
+    cmd.arg(download_script.as_str());
+    wait_for_output(cmd, "download test assets", progress)
+}