Add handler for SIGUSR2 to invoke the debugger.
Add handler for SIGUSR2 to invoke the debugger.

Note that the worker processes are still running while the
debugger is active, and will be spamming log messages at the
terminal. You can kill them with pool.terminate(), but then
you've disrupted the environment you may be debugging.

openaddresses/machine,slibby/machine,openaddresses/machine,slibby/machine,openaddresses/machine,slibby/machine,slibby/machine