Why does the RHEV-M installer fail with error "Engine requires lc_messages to be 'en_US.UTF-8'"?

Issue

• Why does the RHEV-M installer engine-setup fail with the following error message?

Failed to execute stage 'Environment customization': Engine requires lc_messages to be 'en_US.UTF-8'. Please fix lc_messages before you continue.

• The engine database was created observing the required locale settings with the following command:

postgres=# create database engine owner engine template template0 encoding 'UTF8' lc_collate 'en_US.UTF-8' lc_ctype 'en_US.UTF-8';

• The engine database has the required locale settings:

engine=# select datname, datcollate, datctype from pg_database;
       datname        | datcollate  |  datctype   
----------------------+-------------+-------------
 template1            | en_US.UTF-8 | en_US.UTF-8
 template0            | en_US.UTF-8 | en_US.UTF-8
 postgres             | en_US.UTF-8 | en_US.UTF-8
 ovirt_engine_reports | en_US.UTF-8 | en_US.UTF-8
 ovirt_engine_history | en_US.UTF-8 | en_US.UTF-8
 engine               | en_US.UTF-8 | en_US.UTF-8
(6 rows)