Sometime this week we will be removing the `raspberry_pi` theme from the forum. This was deprecated a couple of years ago, and now has very few users (43!), and is effectively unsupported.
All users using this theme will have it changed to the `rpi` theme. I've been using this one for years, and it works well for me!
If you have any problems after the change, please let us know, either by posting on the forums, or email firstname.lastname@example.org.