Replace unknown user login text with something more readable

[dd32]

The error text when you attempt to login with an invalid username isn't very clear:

Unknown username. Check again or try your email address.

"Check Again"? Check what? "Check your email"?

Unlike with an incorrect password (or empty password), the username is also not prefilled which leads to more confusion as the end-user cannot even see that they typo'd their username.

As this is an error message that's intended to be displayed to end-users more often than others, I would suggest that this error message should be far more helpful.

Perhaps something like:

Username Unknown. The username <strong>admin</strong> is not registered on this site. If you're unsure of your username, you can attempt to login using your email address instead.

[SergeyBiryukov]

It looks like the message was improved in [46417] / #43037, but could still use some further clarification.

Let's start by reinstating the "Error:" prefix for consistency. Related: #52914.

[SergeyBiryukov]

In 50589:

Login and Registration: Restore the "Error:" prefix for the "Unknown username" message.

This makes the message more consistent with other error messages related to authentication and registration.

Follow-up to [46417].

Props dd32.
See #52914, #52915.

[audrasjb]

Patch

[audrasjb]

testing the proposed patch

[audrasjb]

Hello,
This is a pretty straightforward patch, but I think it's a good idea to clarify the error. The proposed patch fixes the issue. Let's try this small enhancement for 5.8!

[desrosj]

I like the idea here. But I felt what's currently in the patch is a bit too long. After some discussion in #core, we arrived at "Error: The username X is not registered on this site. If you are unsure of your username, try your email address."

[desrosj]

In 51126:

Login and Registration: Improve the unknown username error message

The new message is more clear and makes the next step more clear to the user.

Props dd32, SergeyBiryukov, audrasjb, desrosj, dlh, marybaum, chanthaboune, jeffpaul.
Fixes #52915.

[lkraav]

Not sure whether core has any copywriting language conventions, but starting sentences with "The" continues to look awkward, mostly creating noise / distraction for minimal value add.

Better: "Username %s ...", so user can immediately see what the problem is, instead of digging through language article soup.