Hi Devrim, we just noticed that barman 1.6.0 doesn't work with psycopg 2.0.14 which is included in rhel6.
Please hold on while we are investigating the best fix.
I've also updated the redmine ticket about that.
Regards,
Marco
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Marco Nenciarini - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
marco(dot)nenciarini(at)2ndQuadrant(dot)it | www.2ndQuadrant.it