Error login when register new author

Hi,

I have search but not find.
I have this particular problem :

I want to register people whith first and last names, and many have accents (like “Jennifer Polié” for exemple).

When I want to create the author in the admin panel, it says “ERROR: This username is invalid. Please enter a valid username.”.

But I have already create logins with accents in wordpress with no problem !… ? So Does someone know why it makes this now ?

Thanks in advance,