To change this setting, edit the LANG value in the file /etc/sysconfig/i18n file.
This is the system file where the Postgres installer gets the locale settings used to create the database.
An example is the following:
After setting this value, then uninstall the existing Postgres, and reinstall the database.
Usually, this error will go away, if this is not the case, then open a Support case to resolve the issue.