chore: checkpoint before Python removal

vendor/thiserror-1.0.69/tests/ui/duplicate-struct-source.rs

@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub struct ErrorStruct {
+    #[source]
+    a: std::io::Error,
+    #[source]
+    b: anyhow::Error,
+}
+
+fn main() {}