Please consider adding PyPy Trove classifiers, because apparently black works fine! At least on the recent PyPy (I tested PyPy3.6 v7.0 on macOS). I used version 18.9b0 of black. See https://pypy.org/download.html

When brace_style is set to AlwaysNextLine then that should also apply to extern blocks. Until recently this config option was only utilized for items, but was recently updated to apply to unsafe blocks and makes sense to do the same for extern

Some relevant places to check in the code:

Perhaps format_extern, w

When I try to beautify the i get the following problem
TypeError: Cannot read property 'on' of undefined

I just installed beautify and uncrustify

https://gist.github.com/ODCA117/917affd6b11437517535a45350379820

I really don't know if we have some rules to create Mercosul/Brazilian license plate, but I think that we should keep support for both (after 2024 we can drop Brazilian support since Brazil will only use Mercosul format).