Pasting into pre blocks loses indentation

If I select and copy a block of Python code, then set up a preformatted-text section in a question statement or part prompt, when I paste the Python code into the pre block all indentation is lost. It doesn't matter where I copy it from. This makes it very difficult to include Python code in questions.

I am using Firefox on Linux.

Reproduce the issue in Firefox on Linux by pasting copied Python code into a preformatted-text section in a question statement or part prompt. Trace the editor's paste handling for pre blocks; done means indentation is preserved regardless of where the code was copied from.

Written by the indexing model from the issue text.