This runs build_tools/style.fish, which runs clang-format on C++, fish_indent on fish and (new) black on python.
If anything is wrong with the formatting, we should fix the tools, but automated formatting is worth it.
A person stuck installing it just for fish on their server
doesn't want to waste time installing the wrong one, so assuage that.
Also tweak to look nicer with 80 columns
As discussed in #5492, it would be good if running fish_config without
Python actually told the user to install Python.
Further, let's give the person some hints on how to configure these
things by hand, since they may have to.
I hate doing this but I am tired of touching a fish script as part of
some change and having `make style` radically change it. Which makes
editing fish scripts more painful than it needs to be. It is time to do
a wholesale reformatting of these scripts to conform to the documented
style as implemented by the `fish_indent` program.
This was causing issues launching fish_config on OS X if fish.app is
renamed to contain a space (noted, but likely not the actual problem,
in issue #3140)
