Ezio: this happens inside a function, like this:

def f():
    canBusType = 'CANdiag'
    result = [eval('canBusType') for i in range(3)]

This is expected, and won't easily fix.  The reason is that list
comprehensions in 3.x use a function namespace "under the hood" (in 2.x,
they were implemented like a simple for loop). Because inner functions
need to know what names to get from what enclosing namespace, the names
referenced in eval() can't come from enclosing functions. They must
either be locals or globals.

Of course, the question to the OP is why eval() is needed anyway.