Improve message in error trying to create user with existing email in multisite

[ernilambar]

Bug Report

• [✓] Yes, I reviewed the contribution guidelines.
• [✓] Yes, more specifically, I reviewed the guidelines on how to write clear bug reports.

Describe the current, buggy behavior

When I try to create user in multisite with existing email address:

wp user create admin1 admin1@gmail.com --role=administrator

Error: <strong>Error:</strong> This email address is already registered. <a href="http://bahu.local/wp-login.php">Log in</a> with this address or choose another one.

Describe what you would expect as the correct outcome

Error: This email address is already registered.

Let us know what environment you are running this on

OS:     Darwin 22.6.0 Darwin Kernel Version 22.6.0: Tue Nov  7 21:48:06 PST 2023; root:xnu-8796.141.3.702.9~2/RELEASE_X86_64 x86_64
Shell:  /bin/zsh
PHP binary:     /usr/local/Cellar/php@8.2/8.2.15/bin/php
PHP version:    8.2.15
php.ini used:   /usr/local/etc/php/8.2/php.ini
MySQL binary:   /usr/local/bin/mysql
MySQL version:  mysql  Ver 8.3.0 for macos13.6 on x86_64 (Homebrew)
SQL modes:
WP-CLI root dir:        phar://wp-cli.phar/vendor/wp-cli/wp-cli
WP-CLI vendor dir:      phar://wp-cli.phar/vendor
WP_CLI phar path:       /Users/nilambarsharma/Sites/bahu
WP-CLI packages dir:    /Users/nilambarsharma/.wp-cli/packages/
WP-CLI cache dir:       /Users/nilambarsharma/.wp-cli/cache
WP-CLI global config:
WP-CLI project config:  /Users/nilambarsharma/Sites/bahu/wp-cli.local.yml
WP-CLI version: 2.10.0

[danielbachhuber]

Seems like a reasonable enhancement 👍