Function is_read_only_error 

pub fn is_read_only_error(err: &Error) -> bool

True when err’s SQLSTATE is 25006 (cannot execute ... in a read-only transaction) – the code the last_used_at update raises when its connection turned read-only mid-query. A local copy of micromegas_ingestion::data_lake_connection::is_read_only_violation’s check: auth doesn’t depend on ingestion.