$duplicity_sub can't handle alphnum characters

In Ubuntu Lucid, duplicity comes in version 0.6.08b, which breaks the current method to analyse the sub-version. Nasty.

I use the Lucid version of backupninja, 0.9.6-4

duplicity --version | /usr/bin/awk '{print $2}'
0.6.08b

/usr/share/backupninja/dup: Zeile 99: [: 08b: Ganzzahliger Ausdruck erwartet.
/usr/share/backupninja/dup: Zeile 105: [: 08b: Ganzzahliger Ausdruck erwartet.
...
/usr/share/backupninja/dup: Zeile 166: [: 08b: Ganzzahliger Ausdruck erwartet.
/usr/share/backupninja/dup: Zeile 208: [: 08b: Ganzzahliger Ausdruck erwartet.
/usr/share/backupninja/dup: Zeile 228: [: 08b: Ganzzahliger Ausdruck erwartet.

(from redmine: created on 2010-03-28, closed on 2010-05-06)