Introduce new style for python extensions

crates/re_types_builder/src/codegen/common.rs

@@ -83,6 +83,15 @@ pub fn remove_old_files_from_folder(folder_path: Utf8PathBuf, filepaths: &BTreeS
             continue;
         }
 
+        if let Some(stem) = filepath.as_str().strip_suffix("_ext.py") {
+            let generated_path = Utf8PathBuf::try_from(format!("{stem}.py")).unwrap();
+            assert!(
+                generated_path.exists(),
+                "Found orphaned {filepath} with no matching {generated_path}"
+            );
+            continue;
+        }
+
         if let Some(stem) = filepath.as_str().strip_suffix("_ext.cpp") {
             let generated_hpp_path = Utf8PathBuf::try_from(format!("{stem}.hpp")).unwrap();
             assert!(