[server] print backend exception if we fail to execute an sql script
It's more useful to see
could not open extension control file "/usr/share/postgresql/9.4/extension/postgis.control": No such file or directory
rather than merely
-> ERROR, skipping /usr/share/cubicweb/cubes/postgis/schema/_ext.postgres.sql
\.svn
^build$
^dist$
\.egg-info$
^.tox$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data.*/database/.*
.*/data/ldapdb/.*
.*/data/uicache/
.*/data/cubes/.*/i18n/.*\.po
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/
^doc/_build
^doc/js_api/