i'm also seeing this in some

@ensure_daemon

testing:

E   returncode: 1
                     E   stdout:
                     E   	
                     E   stderr:
                     E   	WARN] Not watching pantsd pidfile because subprocessdir is outside of buildroot. Having subprocessdir be a child of buildroot (as it is by default) may help avoid stray pantsd processes.
                     E   	Not watching pantsd pidfile because subprocessdir is outside of buildroot. Having subprocessdir be a child of buildroot (as it is by default) may help avoid stray pantsd processes.
                     E   	timestamp: 2019-03-11T00:35:58.099303
                     E   	Exception caught: (builtins.TypeError)
                     E   	  File "/home/cosmicexplorer/tools/pants/src/python/pants/bin/daemon_pants_runner.py", line 313, in post_fork_child
                     E   	    self._raise_deferred_exc()
                     E   	  File "/home/cosmicexplorer/tools/pants/src/python/pants/bin/daemon_pants_runner.py", line 244, in _raise_deferred_exc
                     E   	    raise self._deferred_exception
                     E   	
                     E   	Exception message: exceptions must derive from BaseException
                     ================================================== 1 failed in 23.92 seconds ==================================================

which makes me think that my attempt to fix this exception situation in

_raise_deferred_exc()

might have been at least partially wrong: https://github.com/pantsbuild/pants/pull/7008