Have you ever tried to create a schema with pg_ as the first part of the
name of the schema? If so, you probably didn't get very far. Postgres won't
let you do that. It reserves the pg_ prefix for system schemas. If you try
to create a schema in this way, you'll get an unacceptable schema name
error.
> create schema pg_cannot_do_this;
ERROR: unacceptable schema name "pg_cannot_do_this"
DETAIL: The prefix "pg_" is reserved for system schemas.