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)：
rds permission denied for language c
対処
関連リンク
How to get around the "permission denied for language c" error on ...
https://stackoverflow.com/questions/36434582/how-to-get-around-the-permission-denied-for-language-c-・・・
Cant create postgres base type (with hstore/pgcrypto extensions ...
https://stackoverflow.com/questions/31018547/cant-create-postgres-base-type-with-hstore-pgcrypto-ext・・・
Permission issues with Importing PostgreSQL Dump to RDS
https://stackoverflow.com/questions/25622860/permission-issues-with-importing-postgresql-dump-to-rds・・・
Setting up PostGis on Amazon RDS
https://stackoverflow.com/questions/21838349/setting-up-postgis-on-amazon-rds
ERROR: permission denied for language c
https://stackoverflow.com/questions/7014437/error-permission-denied-for-language-c
ERROR: permission denied for language c - Stack Overflow
https://stackoverflow.com/questions/7014437/error-permission-denied-for-language-c/7014649
postgresql - RDS crosstab: ERROR: permission denied for language c ...
https://dba.stackexchange.com/questions/128691/rds-crosstab-error-permission-denied-for-language-c
PostgreSQL 9.3 Amazon RDS gives error ...
https://dba.stackexchange.com/questions/78768/postgresql-9-3-amazon-rds-gives-error-while-using-uuid・・・
postgresql - Installing a language with Amazon ...
https://dba.stackexchange.com/questions/179944/installing-a-language-with-amazon-rds
permissions - Postgresql enabling extensions ...
https://dba.stackexchange.com/questions/175319/postgresql-enabling-extensions-without-super-user