assert in Lua doesn't handle colon character?

[thehankinator]

The below code:

assert(false, "Why:Does this happen?")

Gives the following result:

"C:/Users/User/Documents/Leadwerks/Projects/MyGame/Addons/THUI/Core.lua" : 80 : Why

If I simply don't use a colon it prints the whole string. What's the deal with the colon character? I don't see anything in PIL for this behavior https://www.lua.org/pil/8.3.html