Hi Sebastian --

> I am having problems with the fontification of python and ipython source
> blocks when the code contains curly brackets "{}" (other course blocks are
> ok). For instance, the following snippet
>
> #+BEGIN_SRC python :results drawer
> import matplotlib.pyplot as plt
> plt.plot([1,2,3])
> plt.show()
> a=1
> print("a={}".format{a})
> #+END_SRC
>
> does not fontify correctly in either python or ipython source blocks.
>
> As a consequence, when exporting the org file to HTML (C-c C-e h h), it
> fails with the following message:
>
> font-lock-fontify-keywords-region: Invalid function: #<subr progn>

I'm unable to reproduce this behavior on emacs 27.1 and git
master. Fontification and export work fine with this code block for me.

Does the error still happen when you use emacs -q ? Or if you use git
master?

Jack