## 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
937de121f3