So I'm going to say what I always say when people complain about semantic whitespace: Your code should be properly indented anyway. If it's not, it's a bad code.
I'm not saying semantic whitespace is superior to brackets or parentheses. It's clearly not. But it's not terrible either.
As someone who codes in Python pretty much everyday for years, I NEVER see indentation errors. I didn't see them back when I started either. Code without indentation is impossible to read for me anyway so it makes zero difference whether the whitespace has semantic meaning or not. It will be there either way.