diff --git a/cherrypy/_cpcompat_subprocess.py b/cherrypy/_cpcompat_subprocess.py
index <HASH>..<HASH> 100644
--- a/cherrypy/_cpcompat_subprocess.py
+++ b/cherrypy/_cpcompat_subprocess.py
@@ -883,7 +883,7 @@ class Popen(object):
                 startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW

                 startupinfo.wShowWindow = _subprocess.SW_HIDE

                 comspec = os.environ.get("COMSPEC", "cmd.exe")

-                args = '{} /c "{}"'.format(comspec, args)

+                args = '{0} /c "{1}"'.format(comspec, args)

                 if (_subprocess.GetVersion() >= 0x80000000 or

                         os.path.basename(comspec).lower() == "command.com"):

                     # Win9x, or using command.com on NT. We need to

@@ -1029,7 +1029,7 @@ class Popen(object):
             elif sig == signal.CTRL_BREAK_EVENT:

                 os.kill(self.pid, signal.CTRL_BREAK_EVENT)

             else:

-                raise ValueError("Unsupported signal: {}".format(sig))

+                raise ValueError("Unsupported signal: {0}".format(sig))

 

         def terminate(self):

             """Terminates the process
Python <I> str.format does not support unindexed parameters

The code using Python <I>+ only code was used on Windows only.

--HG--
branch : subprocess-py<I>-win<I>-fix