Youtube discontinues username login

The last time I logged in to Youtube I was given the message that next time I have to use my email address.

We no longer support signing into your account with your YouTube username—but you can still access your account:

• Enter your email address instead of your YouTube username. Your account has an associated email address. If you’re not sure what it is, see below.
• Your password still works. Your password hasn’t changed—it’s still the same password you’ve been using to sign into YouTube.

You’re still signing into the same account as always—you just need to enter the email address on the account instead of your YouTube username.

More info at Youtube.