Each class must be in its own file, and the execution starts from "public static void main(String[] args)" inside it. Then you have to deal with complex data types very early: python's set of primitives is much richer, which is great when teaching. Also, doing IO in Java is a pain unless you distribute a library.
To those who think Python's significant whitespace is a problem, I think you need to watch an otherwise intelligent beginner struggle with an error on line 80 because they mismatched their braces on line 20. If you aren't properly indenting your code, it becomes an unreadable mess anyways, so why not enforce it at a language level? And if you think an IDE can do this for you, think again. People just complain that it does things wrong when it indents half their methods by 2 extra tabstops because they missed a brace. They don't really get it, they just get into a feedback loop where they say, "Oh, it won't compile. Let me scan the entire program counting braces" which is a waste of everyone's time. I've seen people go entire semesters without ever learning to write readable indented code.
Or like others have said we could hand-wave it away until later.