VM Create prompting for admin username

[derekbekoe]

My admin username was invalid and instead of throwing an error and exiting, it prompted me to enter it. It felt inconsistent with how usually, we simply throw an error.

$ az vm create -g debekoe-a4 -n mytestvm --image UbuntuLTS
Cannot use admin username: root. Admin username should be at least 6 characters and cannot be 'root'
Admin Username: ...

However, when I didn't have an SSH public key available, I received an error and there was no prompt:

An RSA key file or key value must be supplied to SSH Key Value. You can use --generate-ssh-keys to let CLI generate one for you.

If the admin username is invalid, should it not prompt and return an error such as below?

$ az vm create -g debekoe-a4 -n mytestvm --image UbuntuLTS
Cannot use admin username: root. Admin username should be at least 6 characters and cannot be 'root'. Specify admin username with --admin-username.