Can I get a warning always evaluates to true in Python?

I had in my code a bug like this (dt is a string):

if 'char' or 'CHAR' in dt:
    foo = 'ch'

and it took me a while to debug it. If I am correct, the first operand always evaluates to true, which causes the body of the if statement to always execute.

In C++ I would get a warning in some of these cases, making the annihilation of such bugs easy.

Is there any way that I can get Python warn me about these situations, or not (because it gets interpreted or something)?