Installer user name setup, tell the user what characters are not allowed

[mycae]

"who are you" disallows the user to proceed when users enter in an invalid username. This could be easily rectified by displaying the text "please only use lowercase characters for your username" or whatever is appropriate

https://answers.launchpad.net/ubuntu/+source/ubiquity/+question/137916

Note the key quote
"we get this so many times"

[Erick Brunzell (lbsolost)]

If the username includes incorrect characters, specifically CAPS, the installation stalls with no indication why it's stalled.

I'd think an incorrect username should result in the same warning behavior as a short password.

[Matthew Paul Thomas (mpt)]

It's not mentioned in the current installer specification <https://docs.google.com/View?id=dfkkjjcj_101gnkrpg5v#6_2_First_Boot_464401107281446_5590505003929138>, but in the original installer specification from 2005 <https://wiki.ubuntu.com/UbuntuExpress/GnomeUserInterface#Personal%20information>, I suggested that prohibited characters be ignored, and that all other characters be converted to lower case as they are typed. That would avoid the need for any extra instructions, warnings, or error messages.

[Evan (ev)]

Assigning to myself with the intention on implementing Matthew's suggestion.

[Colin Watson (cjwatson)]

The core of this is already fixed in natty; see bug 555896. Obviously I don't mind if we want to go further though.

[Colin Watson (cjwatson)]

(As such, I think it might make sense to close the papercut task on this bug, since the part identified as a papercut is already fixed.)

[Vish (vish)]

We already have bug 549195 , for this issue and it has its own dups too.