A young Afghan vendor waits for customers to buy sheep's heads at a roadside stall at the busy market in Kabul on November 29, 2015. (Photo by Wakil Kohsar/AFP Photo)

A humanoid robot named “Yangyang” shows a facial expression during its demonstration at the Global Mobile Internet Conference (GMIC) 2015 in Beijing, China, April 29, 20155. The android was produced jointly by China's Shanghai Yangyang Intellegent Robot Science Service center and Japanese professor Hiroshi Ishiguro, with the aim of popularising robotics among the young. (Photo by Kim Kyung-Hoon/Reuters)

Actor Cornelius Obonya as Jedermann and actress Brigitte Hobmeier as Buhlschaft perform on stage during a dress rehearsal of Hugo von Hofmannsthal's drama “Jedermann” (Everyman) at Domplatz square in Salzburg, Austria, July 16, 2015. The play is directed by Julian Crouch and Brian Mertes and will premiere as part of the annual Salzburg cultural Festival on July 19, 2015. (Photo by Leonhard Foeger/Reuters)

A dragon mask for the upcoming Lunar New Year hangs on the wall at Lily Hambali's and lion masks and custome maker in Bogor, Indonesia, 02 February 2015. The Chinese Lunar New Year, known here as Imlek, is only three weeks away. The whole city is getting decked out to celebrate the event on 19 February 2015. (Photo by Adi Weda/EPA)

Edibles are displayed at Shango Cannabis shop on first day of legal recreational marijuana sales beginning at midnight in Portland, Oregon October 1, 2015. The sale of marijuana for recreational use began in Oregon on October 1, 2015 as it joined Washington state and Colorado in allowing the sale of a drug that remains illegal under U.S. federal law. (Photo by Steve Dipaola/Reuters)

Pedestrians stop to look at and photograph a DeLorean Motor Company DMC-12 customized to look identical to the car used in the film "Back to the Future Part II" and that will be part of a Lyft promotion in New York, October 21, 2015. In the 1989 movie, main character Marty McFly traveled to the future to October 21, 2015. (Photo by Lucas Jackson/Reuters)

An employee walks near a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. The Borodinsky colliery, 9 km (5.6 miles) long and more than 100 meters (328 feet) deep, annually produces more than 20 million tons of coal and is considered to be the biggest opencast coal mine in Russia, according to official representatives. (Photo by Ilya Naymushin/Reuters)

A Syrian rebel walks past Sham 2, a homemade armored vehicle, in Bishqatin, Syria, on December 8, 2012. From a distance it looks rather like a big rusty metal box but closer inspection reveals a homemade armored vehicle waiting to be deployed. Sham II, named after ancient Syria, is built from the chassis of a car and touted by rebels as “100 percent made in Syria”. (Photo by Herve Bar/AFP Photo)