Ticket #42963: 42963.diff

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

@@ -1179 +1179 @@
                 if ( ! $wp_filesystem->exists( $old_file ) ) {
                         continue;
                 }
-                $wp_filesystem->delete( $old_file, true );
+
+                // If the file isn't deleted, try writing an empty string to the file.
+                if ( ! $wp_filesystem->delete( $old_file, true ) && is_file( $old_file ) ) {
+                        $wp_filesystem->put_contents( $old_file, '' );
+                };
         }
 
         // Remove any Genericons example.html's from the filesystem