You have old files in your logwatch tmpdir (/var/cache/logwatch):
logwatch.rYGXqHov
The directories listed above were most likely created by a
logwatch run that failed to complete successfully. If so, you
may delete these directories.

Logwatchから上記のメールが届く。

# cd /var/cache/logwatch

# ls

logwatch.rYGXqHov

削除するだけ

# rm -rf logwatch.rYGXqHov