Notify administrators of successful, failed, and pending core updates.

Blocks future background updates after critical failures, but allow retries in certain situations. More in the ticket.

fixes #10787.


git-svn-id: https://develop.svn.wordpress.org/trunk@25841 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/update-core.php

@@ -897,6 +897,9 @@ function update_core($from, $to) {
 	// If we made it this far:
 	do_action( '_core_updated_successfully', $wp_version );
 
+	// Clear the option that blocks auto updates after failures, now that we've been successful.
+	delete_site_option( 'auto_core_update_failed' );
+
 	return $wp_version;
 }