function email_exists() check without removing umlauts

[hpr78]

But with wp_insert_user() the umlauts got removed.
A littel bit confusing.

[dots]

We have attached the patch file. It will remove "umlauts" before existing email check.

[binarygary]

Unit Test for 28163

[johnregan3]

Refreshed Test for 28163

[johnregan3]

After updating the Test patch it is apparent that the original patch (user.php.patch) is no longer needed. The sanitize_email() call is now handled in wp-includes/default-filters.php using the 'pre_user_email' filter.

// Email saves.
foreach ( array( 'pre_comment_author_email', 'pre_user_email' ) as $filter ) {
	add_filter( $filter, 'trim' );
	add_filter( $filter, 'sanitize_email' );
	add_filter( $filter, 'wp_filter_kses' );
}