Why do python generators and functions share the "def" keyword?

Consider the following:

def some_function():
    return 1

def some_generator():
    yield 1

In the code above, some_function is a function, while some_generator is a generator. They look quite similar.

The problem that I have when reading code is that I need to scan through every line in a "function" looking for the yield keyword before I can determine whether it is actually a function or a generator!

It just seems to me that using a different keyword for generators would make more sense, e.g.:

gen some_generator():
    yield 1

What are the merits of using the def keyword for both generators and functions? Why has a new keyword is not been introduced to separate functions and generators?