Post-install problem: error when creating a user with caps, clears all new user form

During post-install the first step on the web interface requires creating the first user.

I tried creating a user using capital letters (“MagicFab”). There was an error “Argument ‘username’ incorrect : Doit être composé uniquement de caractères alphanumérique et de tiret bas”.

‘username’ should be shown in French, and the capital letters should be ignored, while avoiding clearing the whole form because of a validation message.

Username need to be in lower-case. The error message will be corrected.

I keep having this error too…