Update affected code so it works with latest version of eventlet.
import os
import shlex
import signal
-import subprocess
from subprocess import list2cmdline
from ctypes import cdll
import six
+# NOTE: eventlet 0.19.0 removed support for sellect.poll() so we not only provide green version of
+# subprocess functionality and run_command
+from eventlet.green import subprocess
from st2common import log as logging
