Kenyan riot police officers raise batons over a man during a demonstration of Kenya's opposition supporters in Nairobi, on May 16, 2016. Opposition protestors led by former Prime Minister Raila Odinga gathered outside the Indepedent Electoral and Boundaries Comission building to demand the dismissal of IEBC commissioners, after alleged bias towards the ruling Jubillee Alliance Party. (Photo by Carl De Souza/AFP Photo)

In this Wednesday, June 8, 2016 photo, Joe Giles, an actor portraying a zombie in “The Walking Dead”, poses with social media reporter Danielle Datu during a walker boot camp at Universal Studios Hollywood in Los Angeles. (Photo by Jae C. Hong/AP Photo)

Skulls are seen at the witch doctor kiosk during the day of offerings to the “Pachamama” (Mother Earth) in El Alto, Bolivia, August 1, 2016. Pachamama is a goddess revered by the indigenous people of the Andes. She is also known as the earth/time mother. In Inca mythology, Pachamama is a fertility goddess who presides over planting and harvesting, embodies the mountains, and causes earthquakes. (Photo by David Mercado/Reuters)

Ostriches wear masks as they are transported by a truck for relocation in Zhengzhou, Henan Province, China, August 8, 2016. (Photo by Reuters/Stringer)

People pause at a memorial set up for victims of a mass shooting in Las Vegas, Nev., on Tuesday, October 3, 2017. A gunman opened fire on an outdoor music concert on Sunday. It was the deadliest mass shooting in modern U.S. history, with dozens of people killed and hundreds injured, some by gunfire, some during the chaotic escape. (Photo by John Locher/AP Photo)

In 2013, the United Nations General Assembly officially designated November 19 as World Toilet Day, which is coordinated by UN-Water in collaboration with governments and partners. Here: An open-air toilet and a hot spring shower are seen in the middle of nowhere on the road to the Krafla geothermal power station and lava fields, near Reykjahlid and Lake Myvatn in northeastern Iceland, on August 19, 2012. (Photo by Mariana Suarez/AFP Photo)

The first four finalists are selected during the 66th Miss Universe pageant at Planet Hollywood hotel-casino in Las Vegas, Nevada on November 26, 2017. (Photo by Steve Marcus/Reuters)

British theoretical physicist Stephen Hawking, Cambridge University Professor and Fellow, circa 1985. Stephen Hawking, the brightest star in the firmament of science, whose insights shaped modern cosmology and inspired global audiences in the millions, has died aged 76. (Photo by Gemma Levine/Getty Images)