Too many cases of bare `except:` and `except Exception:`

[moreati]

There are 40ish lines containing a bare except: or overly broad except Exception. They're probably hiding errors that we don't want to hide

➜  mitogen git:(github-actions) ✗ ag "except:|except Exception" mitogen ansible_mitogen -l | sort
ansible_mitogen/mixins.py
ansible_mitogen/module_finder.py
ansible_mitogen/process.py
ansible_mitogen/runner.py
ansible_mitogen/services.py
ansible_mitogen/target.py
mitogen/compat/pkgutil.py
mitogen/core.py
mitogen/debug.py
mitogen/fork.py
mitogen/master.py
mitogen/parent.py
mitogen/profiler.py
mitogen/service.py
mitogen/setns.py
mitogen/unix.py

refs #694