french translation

Message "This field is required" not transmated when using portal in French


I'm using Community Edition with preference language french.
Most of th UI of the Bonita Portal is translated to french (automatically because french is one of the provided language).
However, when not filling mandatoty inputs, the message "This field is required" is not transmated to french.
This is surprising.
What should I do to get it in frech ?

In advance, thanks for your help.

Best regards,