Bugfixes:
* When cleaning up after failed clone, stat the to-be-cleaned-up
directory before running rmtree on it. Closes:#796773.
+ * Do not call "warn" on failure of cleanup handler in END block
+ (since warn has been made fatal and aborts the cleanup chain).
+ * Print better error message (with `fail' rather than `die') if
+ `dgit clone' cannot create the destination directory.
Test suite:
* When sbuild fails, do not crash due to sed not finding the log