def colon_subscripts(u):
    """
    Array colon subscripts foo(1:10) and colon expressions 1:10 look
    too similar to each other.  Now is the time to find out who is who.
    """
    if u.__class__ in (node.arrayref,node.cellarrayref):
        for w in u.args:
            if w.__class__ is node.expr and w.op == ":":
                w._replace(op="::")
Array colon subscripts foo(1:10) and colon expressions 1:10 look
    too similar to each other.  Now is the time to find out who is who.