pub fn invalid_escape(output: &str, paths: &[&str]) -> Option<String>Expand description
Python’s warning of an invalid escape in one of paths’ own string
literals, from a run’s output (test_x.py:15: SyntaxWarning: "\\|" is an invalid escape sequence): the string holds what its author did not
write (the example’s US3-2, 2026-11-04).