Ident authentication failed for user "postgres"

* **asyncpg version**: 0.20.1
* **PostgreSQL version**: 12
* **Python version**: 3.7.4
* **Platform**: Centos 8
* **Do you use pgbouncer?**: No, what is it?
* **Did you install asyncpg with pip?**: Yes

> asyncpg.exceptions.InvalidAuthorizationSpecificationError: Ident authentication failed for user "postgres"

No source file or test is identified. Start by reproducing the connection failure with asyncpg 0.20.1, PostgreSQL 12, Python 3.7.4, and CentOS 8, then inspect the PostgreSQL authentication configuration and the reported exception. Done requires determining whether the failure is in asyncpg or the server setup, but the issue does not define a code change.

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