U.S. Democratic presidential candidate Hillary Clinton speaks during a campaign event at Temple University in Philadelphia, Pennsylvania, U.S. September 19, 2016. REUTERS/Carlos Barria

Supporters listen to Republican presidential nominee Donald Trump at a rally at High Point University in High Point, North Carolina, U.S. September 20, 2016. REUTERS/Jonathan Ernst

Republican presidential nominee Donald Trump speaks at a rally with supporters at High Point University in High Point, North Carolina, U.S. September 20, 2016. REUTERS/Jonathan Ernst

Nicaragua's Liberal Independent Party (PLI) presidential candidate Jose del Carmen Alvarado and vice presidential candidate Yadira Rios (centre, R) pose for a picture after a news conference in Managua, Nicaragua September 20, 2016. REUTERS/Oswaldo Rivas

The Allergan logo is seen in this photo illustration November 23, 2015. REUTERS/Thomas White/Illustration/File Photo

Russian President Vladimir Putin delivers a speech during a meeting with members of the Russian summer sports Paralympic team at the Kremlin in Moscow, Russia September 19, 2016. REUTERS/Ivan Sekretarev

The new iPhone 7 smartphone is displayed inside an Apple Inc. store in Los Angeles, California, U.S., September 16, 2016. REUTERS/Lucy Nicholson

Signage is displayed outside of Tesla Motors before the Tesla Energy Powerwall Home Battery event in Hawthorne, California April 30, 2015. REUTERS/Patrick T. Fallon