Python REPL code blocks now broken

[treyhunner]

The new rich text editor is breaking all of my Trello cards in one of my boards because they all contain Python REPL output.

For example this:

```pycon
>>> s = S()
>>> s[4]
4
>>> s[3]
3

```

Is turned into this:

```pycon
> \>> s = S()
> \>> s[4]
4
> \>> s[3]
3

```

`>>>` seems to be turned into `> \>>` consistently in all my code blocks. Switching to markdown mode doesn't fix the issue.

Is there any way to disable the new editor or undo the damage it's doing to my cards? Clicking the Edit button seems to trigger this, so I can't currently edit any of my cards or even copy-paste their original markdown without transforming them all into a mess.

[treyhunner]

I just noticed the link below the text field to switch back to the old markdown editor. I'm not sure how the new editor enabled itself, but I've disabled it now and manually fixed the cards that I broke.