The way to deal with a potential lion attack is basically to act like another threatened cat. Even domestic cats have the same basic responses.
Cats expect their prey to run. They also attack when prey isn't facing them. So the first thing you'd need to do is face the lion, stand your ground, and under no circumstances run or back up.
Cats respond to eye contact. Domestic cats blink slowly at us and one another as a non-threatening gesture that everything is ok. So when dealing with a lion, you'd need to make direct eye contact and fixate your gaze. This is cat for 'do not mess with me because I am ready to fight'.
The next thing you'd do is show the lion you are preparing for an actual fight. Domestic cats fluff up their fur, turn sideways, and flatten their ears, and growl and hiss. They do this to make themselves appear larger. Since humans are taller than a lion on its four legs you already look intimidating. You then turn side on, keeping your eyes fixed, widen your stance, raise your arms, and clap and shout. This is about as close as we can get to behaving like we are ready to fight.
Lions will make a few charges to get prey to run. If you stand your ground, they might eventually back off ... you're not worth the hassle if there is other prey around. If a lion does attack, there is very little we can do to defend ourselves ... all we can do in the absence of weapons is make ourselves look like too much effort to be worth it.