konsti 937de121f3 check-formatter-stability: Remove newlines and add --error-file (#5491) ...

## Summary

This makes the output of `check-formatter-stability` more concise by
removing extraneous newlines. It also adds a `--error-file` option to
that script that allows creating a file with just the errors (without
the status messages) to share with others.

## Test Plan

I ran it over CPython and looked at the output. I then added the
`--error-file` option and looked at the contents of the file

2023-07-04 07:54:35 +00:00

..

src

check-formatter-stability: Remove newlines and add --error-file (#5491)

2023-07-04 07:54:35 +00:00

Cargo.toml

Use rayon to parallelize the stability check

2023-06-30 10:05:25 +02:00