* pg: Re-export DatabaseError from 'pg-protocol'
Before, users would have to import DatabaseError from 'pg-protocol'. If
there are multiple versions of 'pg-protocol', you might end up using the
wrong one.
Closes#2378
* Update error-handling-tests.js
* Update query-error-handling-tests.js
Co-authored-by: Brian C <brian.m.carlson@gmail.com>