dummyssh: use subprocess instead of os.call

Welcome in 2020

Differential Revision: https://phab.mercurial-scm.org/D11082

tests/dummyssh

@@ -1,26 +1,27 b''
 #!/usr/bin/env python3
 
 from __future__ import absolute_import
 
 import os
+import subprocess
 import sys
 
 os.chdir(os.getenv('TESTTMP'))
 
 if sys.argv[1] != "user@dummy":
     sys.exit(-1)
 
 os.environ["SSH_CLIENT"] = "%s 1 2" % os.environ.get('LOCALIP', '127.0.0.1')
 
 log = open("dummylog", "ab")
 log.write(b"Got arguments")
 for i, arg in enumerate(sys.argv[1:]):
     log.write(b" %d:%s" % (i + 1, arg.encode('latin1')))
 log.write(b"\n")
 log.close()
 hgcmd = sys.argv[2]
 if os.name == 'nt':
     # hack to make simple unix single quote quoting work on windows
     hgcmd = hgcmd.replace("'", '"')
-r = os.system(hgcmd)
+r = subprocess.call(hgcmd, shell=True)
 sys.exit(bool(r))