A French riot police officer is surrounded by flames, during a demonstration against the controversial labour reforms of the French government in Paris on September 15, 2016. Opponents of France's controversial labour reforms took to the streets on September 15, 2016 for the 14th time in six months in a last-ditch bid to quash the measures that lost the Socialist government crucial support on the left. Scores of flights in and out of France were cancelled as air traffic controllers went on strike to try to force the government to repeal the changes that became law in July. (Photo by Thomas Samson/AFP Photo)

The moon rises behind the skyline and financial district in Toronto, November 25, 2015. (Photo by Mark Blinch/Reuters)

Boards stand lined up at the Rocinha Surf Association, ASR, headquarters at Rocinha slum in Rio de Janeiro, Brazil, Thursday, July 2, 2015. ASR has given free lessons to over 2,000 children from Rio's shantytowns in the hopes of keeping the boys, who are mostly in their early teens and a few girls occupied by the sport and off the streets. (Photo by Felipe Dana/AP Photo)

Residents make their way along a fence as they try to cross a flooded street after heavy rainfall hit Wuhan, Hubei province, China, July 23, 2015. Severe downpours hit the city on Thursday, flooding streets and shutting down public transportations, local media reported. (Photo by Reuters/China Daily)

A wide-angle view shows the ascent of the shuttle Challenger on January 28, 1986. In the seconds after ignition, the rocket engines' hot blast began the process of destruction. (Photo by NASA)

Female of pygmy hippopotamus called Malaya from Netherlands in zoo in Dvur Kralove nad Labem, Czech Republic, February 22, 2016. (Photo by David Tanecek/CTK via ZUMA Press)

A small section of the expanding remains of the Veil Nebula, a massive star that exploded about 8,000 years ago. The entire nebula is 110 light-years across, covering six full moons on the sky as seen from Earth, and resides about 2,100 light-years away in the constellation Cygnus, the Swan. (Photo by Reuters/NASA/ESA/Hubble)

Li Guoqiang talks on his phone outside his house at Guangfuli neighbourhood, in Shanghai, China, April 1, 2016. Li, 38, is a deliveryman who rents a place at Guangfuli. In a corner of Shanghai, surrounded by a cement wall, lies one of the world's most valuable fields of debris and garbage. On paper, the Guangfuli neighbourhood is a real estate investor's dream: a plot in the middle of one of the world's most expensive and fast-rising property markets. But the reality is more like a developer's nightmare, thanks to hundreds of people living there who have refused to budge from their ramshackle homes for nearly 16 years as the local authority sought to clear the land for new construction. (Photo by Aly Song/Reuters)