If you get this error after finishing the order.:
Attempted to call an undefined method named "getLocale" of class "Language".
Did you mean to call "getLocaleByIso"?
The reason is, that you are using version of module ps_emailalerts 2.2.2 or higher on Prestashop version 1.7.0 - 22.214.171.124.
To fix it, either use older version of module 2.2.1.