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(Reading database ... 404522 files and directories currently installed.)
Removing postgresql-contrib-9.1 (9.1.15-0ubuntu0.12.04) ...
/var/lib/dpkg/info/postgresql-contrib-9.1.prerm: 11: /var/lib/dpkg/info/postgresql-contrib-9.1.prerm: remove_contrib_version: not found
dpkg: error processing package postgresql-contrib-9.1 (--remove):
 subprocess installed pre-removal script returned error exit status 127
Errors were encountered while processing:
 postgresql-contrib-9.1
E: Sub-process /usr/bin/dpkg returned an error code (1)