A masked Burundian protester faces soldiers in front of a burning barricade during an anti-government demonstration against President Pierre Nkurunziza's bid for a third term in the capital Bujumbura, Burundi, 25 May 2015. Street protests continued on 25 May as the United Nations Secretary-General Ban Ki-moon condemned the killing of the leader of the oppsition party Union for Peace and Development (UPD) Zedi Feruzi who opposed Nkurunziza's bid. (Photo by Dai Kurokawa/EPA)

A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

Employees stand near an airframe for the second Antonov-225 Mriya plane at Antonov aircraft plant in Kiev, Ukraine, September 7, 2016. Ukraine hopes to attract $500 million of investment from China to complete an updated version of the world's biggest aircraft, the Antonov-225 Mriya, the president of manufacturer Antonov said on Wednesday. (Photo by Valentyn Ogirenko/Reuters)

Peasants in the re-taken Somme District work in the fields, circa 1916- 1917, in this Library of Congress handout photo. For women 100 years ago, opportunities to work beyond the home and take part in political life were very limited. As the 20th century progressed, hard-won progress included gradually improved voting rights, while the upheaval of war pushed doors ajar as women worked as part of the war effort. U.S. Library of Congress archive photos show women's workplaces ranging from a flour mill in England to a coal mine in Belgium or Lincoln Motor Co.'s welding department in Detroit. International Women's Day is celebrated on March 8. (Photo by Reuters/Bain Collection/Library of Congress)

A 20 metre high spiral staircase in a tower used as an emergency exit, is seen inside a Federal Reserve bank (Bundesbank) bunker, prior to the bunker's official opening to the public in Cochem, Germany, March 18, 2016. West Germany's Central Bank (Deutsche Bundesbank) stored some 20 billion German marks of emergency notes in two underground bunkers, one in Frankfurt the other in Cochem, between 1964-1988 during the cold war. (Photo by Kai Pfaffenbach/Reuters)

Children clean the interior of a granary in preparation for grain storage in Odek village, north of Uganda capital Kampala February 14, 2015. Odek is the birthplace of Joseph Kony, founder and leader of the rebel group Lord's Resistance Army. The LRA rose up against the government in northern Uganda under the leadership of Kony in the late 1980s and has been accused of abducting children to serve as fighters and s*x slaves. (Photo by James Akena/Reuters)

Attendees look at Volkswagen's BUDD-e, a long distance electric vehicle, displayed during a press event at CES 2016 at The Chelsea at The Cosmopolitan of Las Vegas on January 5, 2016 in Las Vegas, Nevada. CES, the world's largest annual consumer technology trade show, runs from January 6-9 and is expected to feature 3,600 exhibitors showing off their latest products and services to more than 150,000 attendees. (Photo by David Becker/Getty Images)

Journalists (L) walk along the new Caminito del Rey (The King's Little Pathway) in El Chorro-Alora, near Malaga, southern Spain March 15, 2015. Dubbed by many media outlets as the world's scariest pathway, the three-kilometre long pathway, which was built at about 100 metres (330 ft) above the gorge of Los Gaitanes between the years of 1901 and 1905, was closed in 2001 after five people died. A new walkway has then been built over the old walkway and will open to the public on March 28, 2015. (Photo by Jon Nazca/Reuters)