• Commit DB-API 2.0 ClientCannotConnect exception correction.
• Eliminate types-as-documentation annotations.
• Add Connection.transaction alias for asyncpg consistency.
• Eliminate multiple inheritance in postgresql.api in favor of ABC registration.
• Add support for PGTEST environment variable (pq-IRI) to improve test performance and to aid in cases where the target fixture is already available. This should help for testing the driver against servers that are not actually postgresql.