o arduino não consegue fazer o download da biblioteca
"Arduino files are found in 3 locations: The installation folder, the sketchbook folder, and the Arduino15 folder. The installation folder should be removed when you uninstall but the other two folders remain so you will need to remove those also to get a completely clean install. The Arduino15 folder is located at:On Mac OS X:/Users/(username)/Library/Arduino15On Windows:Arduino IDE 1.6.5r5 and previous:C:\Users\(username)\AppData\Roaming\Arduino15Arduino IDE 1.6.6 and later:C:\Users\(username)\AppData\Local\Arduino15 "
http://arduino.esp8266.com/versions/2.5.0/package_esp8266com_index.jsonEsse é o link actual que eu uso no Gestor de placas.Testa, pf
Em anexo, mais uma ajuda.