Hackish - Prevent username with spaces in it - WordPress

example.php

<?php

add_filter( 'pre_user_login', function( $user_login ) {
  if( strpos( trim( $user_login ), ' ' ) !== false ) {
    add_filter( 'gettext', function( $translation, $text ) {
      if( $text === 'Cannot create a user with an empty login name.' )
        return __( "You're not allowed to have spaces in your username" );
      
      return $translation;
    }, 20, 2 );
    
    return '';
  }
  
  return $user_login;
});