Test failure on WP trunk - Invalid Sidebar #32
Description
Tests currently fail on WP trunk:
01. $ wp widget add search sidebar-2 --title="Quick Search"
Error: Invalid sidebar.
https://travis-ci.org/wp-cli/widget-command/jobs/522781350#L669-L689
At first sight, seems to be different than #31
Related wp-cli/wp-cli#5192