A journalist who disappeared last month in Mali's northern city of Gao appeared in a video today, appealing to authorities to do everything they can to free him from Islamist militants holding him. "I'm Olivier Dubois. I'm French. I'm a journalist. I was kidnapped in Gao on April 8 by the JNIM (al Qaeda North Africa). "I'm speaking to my family, my friends and the French authorities for them to do everything in their power to free me," Dubois said in a 21-second video shared on social media. French civilians have long been favoured targets for kidnapping by criminal and…