PYTHON prime numbers function

I am new to programming and I face an issue while trying to write a program in finding out prime number. Here is my code:

def is_prime(x):
    if x < 2:
        return False
    elif x == 2:
        return True
    else:
        for n in range (2,x-1):
            if x % n == 0:
                return False
            else:
                return True

I received an error stating "Your function fails on is_prime(3). It returns None when it should return True."

Can someone please explain the flaw in this code?

Thank you!