Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

An aerial view shows the 11/19 pit and twin slag heaps at the former coal mine site in Loos-en-Gohelle, northern France, November 1, 2015. Loos-en-Gohelle, a town of 7000 inhabitants in the North of France, marked by the closure of coal mines in 1970, has demonstrated a successful transition from coal to a green economy. (Photo by Pascal Rossignol/Reuters)

Howard Jackson, a Liberian migrant, poses for a portrait in the Andalusian capital of Seville, southern Spain March 7, 2016. Jackson escaped civil war and spent three years crossing Africa before reaching Spain. Dressed up in one of his more than 200 costumes, from Peter Pan to Little Red Riding Hood, he is a well-known figure at an intersection entering the Spanish city of Seville where he has sold tissues to motorists for over a decade. Jackson is studying law and wants to become a judge. (Photo by Marcelo del Pozo/Reuters)

In this April 2, 2016 photo, dusty sculptures made of cast-off baby dolls sit in an open-air museum and art workshop off a trash-strewn street cutting through some of the poorest neighborhoods in Port-au-Prince, Haiti. They were created by Haitian artists called Atis Rezistans who have become celebrated in the international art world by creating sculptures out of scrapped car parts, old wood, discarded toys and even human skulls found scattered outside crumbling mausoleums. (Photo by David McFadden/AP Photo)

The Luminous Lantern Parade on June 10, 2016 in Brisbane, Australia. The Luminous Lantern Parade was held at Brisbane’s South Bank on Friday, featuring a parade of glowing animals and characters of all shapes and sizes lighting up the night sky. (Photo by Glenn Hunt/Getty Images)

Georgian men take a break from selling fruit and vegetable at a street market in Tbilisi, Georgia, Wednesday, July 20, 2016. (Photo by Shakh Aivazov/AP Photo)

A woman loyal to the Houthi movement holds a rifle as she takes part in a parade to show support to the movement in Sanaa, Yemen September 6, 2016. The Saudi-led Arab coalition launched a military campaign against the Huthis and their allies in March 2015, after the rebels closed in on Gulf-backed President Abedrabbo Mansour Hadi in his southern refuge of Aden, forcing him into exile. (Photo by Khaled Abdullah/Reuters)