message: Put xml in markdown block to avoid doctest failure
diff: #![allow(dead_code)]
  /// The XML structure for a cobatura report is roughly as follows:
  -///
  +/// ```xml
  /// <coverage lines-valid="5" lines-covered="0" line-rate="0.0" branches-valid="0"
  /// branches-covered="0" branch-rate="0.0" version="1.9" timestamp="...">
  /// <sources>
  /// ...
  /// </packages>
  /// </coverage>
  +/// ```
  use std::error;
  use std::fmt;
  