Ask user for agreeing to data set licenses.

def prompt_user(prompt):
    """Ask user for agreeing to data set licenses."""
    # raw_input returns the empty string for "enter"
    yes = set(['yes', 'y'])
    no = set(['no','n'])

    try:
        print(prompt)
        choice = input().lower()
        # would like to test for exception here, but not sure if we can do that without importing IPython
    except:
        print('Stdin is not implemented.')
        print('You need to set')
        print('overide_manual_authorize=True')
        print('to proceed with the download. Please set that variable and continue.')
        raise


    if choice in yes:
        return True
    elif choice in no:
        return False
    else:
        print(("Your response was a " + choice))
        print("Please respond with 'yes', 'y' or 'no', 'n'")