Comment 34 for bug 1374759

In my case these same errors are happening when trying to probe a Windows recovery partition on a dual boot system. I've worked around this bug by adding the following content to /usr/lib/os-probes/00skip-unknown:

#!/bin/sh
# Skip unknown partitions to avoid syslog errors
set -e
partition="$1"

. /usr/share/os-prober/common.sh

if [ "$partition" = /dev/<your-recovery-partition-here> ]; then
 debug "$partition is a Windows recovery partition; skipping"
 exit 0
fi

# No tests found anything.
exit 1