Ignore psqlrc when loading the rubygems database dump

The SQL dump contains ownership instructions that can't be run if you don't have the right users in your database clusters. When someone has a psqlrc with ON_ERROR_STOP, this fails the load of the dump.

Use the opportunity to trigger an exception when psql returns a non-zero exit code, rather than continue with an empty/inconsistent database.

Test Plan

tested on my laptop with a .psqlrc, the loading doesn't crash anymore

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Migrated from D8914 (view on Phabricator)