Dear Maintainer,

when using rdiff-backup's compare action it reports the following error
message when the source directory has newer or changed files compared to
the backup dir: "ERROR: Action compare failed on step run"

This behaviour can be easily reproduced by doing:

$ mkdir source target
$ cd source/
$ for file in file1 file2 file3; do head -c 1K /dev/urandom > $file; done
$ cd ..
$ rdiff-backup backup source/ target/

Now if the files have not changed it reports:

$ rdiff-backup compare source/ target/
NOTE: No changes found. Directory matches archive data.

However if one changes the modification time of one file

$ touch source/file1
$ rdiff-backup compare source/ target/
changed: file1
ERROR: Action compare failed on step run



I assume that this behaviour is a bug, either the error is reported
mistakenly or the new version of rdiff-backup does not only list changed
files on the compare action but tries to do something afterwards which
fails.

Thanks for maintaining rdiff-backup

Marcel