[Solved] Unable to find optional library: org.apache.http.legacy

Please check if you have android-sdk-windows\platforms\android-23\optional\optional.json file in place. If not then just reinstall API 23 (remove and install again). you can reinstall on sdk manager, uninstall api 23 and install it again, and make sure there optional.json file inside optional folder for android-23.

if not, you can download optional.json file here.