Long ago, I submitted an issue:
        https://github.com/kimchi-project/kimchi/issues/1170 ...
Test by following script:
import subprocess

          import os

          import time

          

          def _check_remote_libvirt_conn(remote_host,

                  user='root', transport='ssh'):

          

              FNULL = open(os.devnull, 'w')

              dest_uri = 'qemu+%s://%s@%s/system' % (transport, user,
          remote_host)

              cmd = ['virsh', '-c', dest_uri, 'list']

              proc = subprocess.Popen(cmd, stdout=FNULL, stderr=FNULL,

                      shell=True, preexec_fn=os.setsid)

              timeout = 0

              while proc.poll() is None:

                  time.sleep(1)

                  timeout += 1

                  if timeout == 5:

                      print("killed")

                      os.killpg(os.getpgid(proc.pid), signal.SIGTERM)

          

          if __name__ == '__main__':

              _check_remote_libvirt_conn('localhost')
`proc` is timeout every time although the connection is
        normal tested by `virsh -c <uri>` list 

      


      
The following is the reason of changing(From Python Document
        2.7.14):

      
 Do not use stdout=PIPE or stderr=PIPE with this function as
        that can deadlock based on the
        child process output volume. Use Popen with the communicate()
        method when you need pipes.
 Using shell=True can be a security
          hazard. See the warning under Frequently Used Arguments
        for details.

      
At the same time, if not change, it does not work.

diff --git a/model/vms.py b/model/vms.py


      
index 6da4f3b..92e771f 100644


      
--- a/model/vms.py


      
+++ b/model/vms.py


      
@@ -1885,10 +1885,11 @@ class VMModel(object):


      
     def _check_remote_libvirt_conn(self, remote_host,


      
                                    user='root',
        transport='ssh'):


      
 


      
+        FNULL = open(os.devnull, 'w')


      
         dest_uri = 'qemu+%s://%s@%s/system' %
        (transport, user, remote_host)


      
         cmd = ['virsh', '-c', dest_uri, 'list']


      
-        proc = subprocess.Popen(cmd,
        stdout=subprocess.PIPE,


      
-                                shell=True,
        preexec_fn=os.setsid)


      
+        proc = subprocess.Popen(cmd, stdout=FNULL,
        stderr=FNULL,


      
+                                shell=False,
        preexec_fn=os.setsid)


      
         timeout = 0


      
         while proc.poll() is None:


      
             time.sleep(1)
-- 
Regards
River (Fu.Lin)