Warning: Cannot modify header information…

So what do you call it when you are just trying to change your blog tagline and you hit SAVE and get:

Warning: Cannot modify header information – headers already sent by (output started at /home/content/r/i/d/ridgelyschantz/html/zoo/radixaster/wp-includes/pluggable.php:1) in /home/content/r/i/d/ridgelyschantz/html/zoo/radixaster/wp-includes/pluggable.php on line 740

Here’s the thing: I looked this issue up earlier and common wisdom said “check for unintentional spaces before <?php and after ?>. Even though I have gone through pluggable.php with a finetooth comb on notepad and removed ALL spaces, I still got that error. Here are lines 719-741 as shown in an EditPlus text editor:

if ( !function_exists('wp_redirect') ) :
/**
* Redirects to another page, with a workaround for the IIS Set-Cookie bug.
*
* @link https://support.microsoft.com/kb/q176113/
* @since 1.5.1
* @uses apply_filters() Calls 'wp_redirect' hook on $location and $status.
*
* @param string $location The path to redirect to
* @param int $status Status code to use
* @return bool False if $location is not set
*/

function wp_redirect($location, $status = 302) {global $is_IIS;
$location = apply_filters(‘wp_redirect’, $location, $status);
$status = apply_filters(‘wp_redirect_status’, $status, $location);
if ( !$location ) // allows the wp_redirect filter to cancel a redirect
return false;
$location = wp_sanitize_redirect($location);
if ($is_IIS ){header(“Refresh:0;url=$location”);} else {
if (php_sapi_name()!=’cgi-fcgi’) status_header($status);//This causes problems on IIS and some FastCGI setups
header(“Location: $location”);}} endif;
if ( !function_exists(‘wp_sanitize_redirect’)) :`