このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
could not translate host name
対処
関連リンク
AWS RDS: How to Connect to Instance - Stack Overflow
https://stackoverflow.com/questions/20207006/aws-rds-how-to-connect-to-instance
Connecting to AWS Postgres Instance For Django Backend
https://stackoverflow.com/questions/48313393/connecting-to-aws-postgres-instance-for-django-backend
Amazon RDS Postgres name or service not known
https://stackoverflow.com/questions/34024720/amazon-rds-postgres-name-or-service-not-known
Can't connect to RDS through EC2
https://stackoverflow.com/questions/34300491/cant-connect-to-rds-through-ec2
Occasional Postgres error on Heroku: could not translate host ...
https://stackoverflow.com/questions/12165076/occasional-postgres-error-on-heroku-could-not-translate・・・
PostgreSQL - EC2からRDB(postgresql)にアクセスできない｜teratail
https://teratail.com/questions/43534
could not translate host name "xxx.us-east-1.rds.amazonaws.com" to ...
https://github.com/psycopg/psycopg2/issues/659
could not translate host name "postgres" to address: nodename nor ...
https://github.com/instructure/lti_tool_provider_example/issues/4
postgresql - Posgres Could not translate hostname - Super User
https://superuser.com/questions/982778/posgres-could-not-translate-hostname
PostgreSQL could not translate host name - Dev Shed Forums
http://forums.devshed.com/postgresql-help-21/postgresql-translate-host-name-873179.html