cubicweb #2235595 cubicweb db-dump creates an empty file when something goes wrong [open]

When I do this

$ cubicweb-ctl db-dump myapp
pg_dump -Fc --port=5433 --username=arthur --no-owner --file /tmp/tmp6bFo0z/system myapp
pg_dump: server version: 9.0.4; pg_dump version: 8.4.10
pg_dump: aborting because of server version mismatch
   [Failed] Continue anyway? [y/N/a(bort)/s(hell)]: n
-> error trying to backup system [Failed command: ['pg_dump', '-Fc', '--port=5433', '--username=arthur', '--no-owner', '--file', '/tmp/tmp6bFo0z/system', 'myapp']]
Continue anyway? [y/N/a(bort)/s(hell)]: n

Although I said "no", it still creates an myapp-2012-03-05_21-02-32.tar.gz empty file.

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