Ticket #19883: 19883.diff

wp-admin/includes/class-wp-upgrader.php

@@ -933 +933 @@
                 $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
                 $this->strings['unpack_package'] = __('Unpacking the update&#8230;');
                 $this->strings['copy_failed'] = __('Could not copy files.');
+                $this->strings['copy_failed_space'] = __('Could not copy files. You may have run out of disk space.' );
         }
 
         function upgrade($current) {
@@ -985 +986 @@
 
                 require(ABSPATH . 'wp-admin/includes/update-core.php');
 
+                if ( ! function_exists( 'update_core' ) )
+                        return new WP_Error( 'copy_failed_space', $this->strings['copy_failed_space'] );
+
                 return update_core($working_dir, $wp_dir);
         }