Use original error in case role is missing for Postgres

[trafium]

First of all, I want to thank developers and maintainers for all the good work 👍

We encountered the problem described in #537 while configuring Github Actions for our tests. Pull request was closed without any further info. The problem itself was easily fixed by providing the correct database url, but it took a while to find the source of issue.

[adam12]

I think we could resurrect #537.