Get argument as unicode string from argparse in Python 2 and 3
You can define unicode for Python3 when you get a NameError.
You should make a small note that explains unicode is not defined in Python3, rather than having the user guess, what #py3 means.

try:
    unicode
except NameError:
    # Define `unicode` for Python3
    def unicode(s, *_):
        return s


You should use the type parameter to add_argument, to change the type returned.
And so if you don't want to have unicode in the global scope in your Python3 environment you can bind it to that functions scope.

def build_to_unicode():
    try:
        unicode
    except NameError:
        def unicode(s, *_):
            return s

    def inner(s):
        return unicode(s, "utf-8")

    return inner

to_unicode = build_to_unicode()


Also your lack of a definitive style to pass variables to the parser made it harder for me to read your code.

try:
    unicode
except NameError:
    # Define `unicode` for Python3
    def unicode(s, *_):
        return s

def to_unicode(s):
    return unicode(s, "utf-8")

parser = argparse.ArgumentParser(
    description='Organize your movie collection using symbolic links')
parser.add_argument(
    'media_src',
    metavar='FILE|DIR',
    help='Media file or directory',
    type=to_unicode)

args = parser.parse_args(args=argv[1:])
# If you really want to.
args = vars(args)