message: Handle backslash-escaped backslashes
diff: @@ -1188,6 +1188,9 @@ enum MatchKind {
  /// See `substitute_macros` for a complete list of macros.
  pub fn lines_match(expected: &str, actual: &str) -> bool {
  // Let's not deal with / vs \ (windows...)
  + // First replace backslash-escaped backslashes with forward slashes
  + // which can occur in, for example, JSON output
  + let expected = expected.replace("\\\\", "/");
  let expected = expected.replace("\\", "/");
  let mut actual: &str = &actual.replace("\\", "/");
  let expected = substitute_macros(&expected);
  