util: Change the /tmp/printer pty to be group readable

For some reason, Linux creates the pseudo tty with group writable
permissions, but not group readable.  Use chmod to allow the device to
also be group readable.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/util.py

@@ -29,7 +29,9 @@ def create_pty(ptyname):
         os.unlink(ptyname)
     except os.error:
         pass
-    os.symlink(os.ttyname(sfd), ptyname)
+    filename = os.ttyname(sfd)
+    os.chmod(filename, 0660)
+    os.symlink(filename, ptyname)
     set_nonblock(mfd)
     old = termios.tcgetattr(mfd)
     old[3] = old[3] & ~termios.ECHO