Werewolves.com: Werecats: The Lions of Tsavo:
In Africa, however, werecats and large felines are honored as kings; the ability for humans to shapeshift into feline form is a sign of royalty, –or even of a god or goddess. The best example of this traditional belief is shown in Africa’s historical, real life creatures “the man-eaters of Tsavo.” [...] The native railroad workers believed the lions were reincarnated African kings who were trying to stop the invading Europeans by making it impossible for them to build the railroad.
And that's all the info that Wikipedia has about the African werelion, since they use that sole source. And with such vagueness, I'm leaning to the idea that African werelions were made up this century or so.
But I want to know if it was only invented this century or the previous, or if it really was from pre-colonial African folklore, or thereabouts. If so, I'd like at least written attestations that such myths existed.
And if there are any such gods that can turn into lions and humans and back, Wikipedia's list of Lion Deities doesn't have anyone useful. They're basically all Egyptian or Hindu.