default file creation when using reactor.spawnProcess

I'm attempting to move over PERL code to python code using the twisted
framework.
so far a few hiccups but this mailing list has helped me quite figure it out.

I have a few few more hurdles, one being that since moving from Perl's

my $cmd = "xvfb-run --auto-servernum firefox -P $profile_id";
$pid = open2($infh, $outfh, $cmd);

to twisted's reactor.spawnProcess:

 subprocess = reactor.spawnProcess(self.pp, args[0], args, env =
os.environ, usePTY=1, childFDs=None)

when the xvfb/firefox processes create files they do so with root
read/write, owner no permissions and group
no permissions,

using the the perl implementation the twisted daemon is run as a
particular user and the file creation via firefox is rw rw rw which is
what  my goal is.

What code would help those on the list willing to help? the daemon
script code in init.d?

Thanks in advance, so far this list has been golden!
Stephan