Every time I try to get the aria label attribute, I've run into this issue before and the question on here addressing it doesn't help at all. I've tried sleep, and list comprehensions (I honestly don't know why that would make it work), but that's where I'm at right now and my brain is jelly :). Can't use xpath if that's what you want to suggest btw
messages = driver.find_elements_by_class_name('DMBLb')
buttons = message.find_elements_by_class_name('wpO6b')
for button in buttons:
option_buttons = button.get_attribute('aria-label')
print(option_buttons) # returns none