sysutils/py-supervisor: Update to 4.2.1

[otis]

Summary

Update sysutils/py-supervisor to 4.2.1

Changelog for 4.2.1:

• Fixed a bug on Python 3 where a network error could cause supervisord to crash with the error <class 'TypeError'>:can't concat str to bytes.
• Fixed a bug where a test would fail on systems with glibc 2.3.1 because the default value of SOMAXCONN changed.

And while I'm here, also clean some style nits.

[osa]

Looks good to me.