Syrian Internal Security Forces dance in celebration during their graduation ceremony, at Ain Issa desert base, in Raqqa province, northeast Syria, Thursday, July 20, 2017. Some 250 residents of Syria's Raqqa province are the latest batch to graduate from a brief U.S-training course that is preparing an internal security force to hold and secure areas as they are captured from Islamic State militants. (Photo by Hussein Malla/AP Photo)

A woman affected by tear gas is assisted during a May Day protest against austerity measures, in San Juan, Puerto Rico May 1, 2018. (Photo by Alvin Baez/Reuters)

Cambridge students the morning after the Trinity and Jesus college May Balls in Cambridge, United Kingdom on June 19, 2018. Students at Cambridge University celebrate the end of the academic year with the May Balls. (Photo by South West News Service)

Long row of shiny new Flying Fortresses, part of huge reserves being built up in Britain for D-Day, stands by to be flown to combat units as replacements, May 25, 1944. (Photo by AP Photo)

A commercial airline landing at the Princess Juliana International Airport in St Maarten on July 9, 2018. Ukrainians Oleg Kolisnichenko, 36, and Yulia Nos, 25, have been blasted for the “stupid stunt” on Maho Beach, which lies next to the main airport on the Caribbean island of Saint Martin. The stunt was met with criticism rather than praise from social media users. (Photo by SWNS: South West News Service)

A man walks inside the flooded Cochin international airport after the opening of Idamalayar, Cheruthoni and Mullaperiyar dam shutters following heavy rain, on the outskirts of Kochi, India, August 15, 2018. (Photo by Sivaram V/Reuters)

Migrants try to board a truck at Ouistreham ferry port in the hope of reaching the UK on September 12, 2018 in Ouistreham, France. After the clamp down at Calais many young migrants are seeking out new routes to the United Kingdom as stowaways on vehicles making the channel crossing by ferry from French ports. The migrants, of mostly African origin, camp out on the roadside and woodland areas as the authorities prevent the setting up of any camps. (Photo by Christopher Furlong/Getty Images)

Devotees of the Chinese Jui Tui shrine are seen with spikes piercing their cheeks during a procession celebrating the annual vegetarian festival in Phuket, Thailand in this October 19, 2015 combination photo. The festival, featuring face-piercing, sacrifice, spirit mediums and strict vegetarianism celebrates the local Chinese community's belief that abstinence from meat and various stimulants during the ninth lunar month of the Chinese calendar will help them obtain good health and peace of mind. (Photo by Jorge Silva/Reuters)