output.py: consistently use sys.__stderr__

sys.stderr is sometimes temporarily replaced by other objects, thus rely
on sys.__stdserr__ consistently. Also provide a default for `fd` in
`init_curses()`.

lib/portage/output.py

@@ -292,7 +292,7 @@ def init_xterm_titles():
  try:
  # by default check if we can dynamically query the proper title
  # setting sequence via terminfo
- curses = init_curses(sys.stderr)
+ curses = init_curses()
 
  if curses is not None:
  tsl = curses.tigetstr("tsl").decode()
@@ -334,7 +334,7 @@ def xtermTitle(mystr, raw=False):
  mystr = _unicode_encode(
  mystr, encoding=_encodings["stdio"], errors="backslashreplace"
  )
- f = sys.stderr.buffer
+ f = sys.__stderr__.buffer
  f.write(mystr)
  f.flush()
 
@@ -547,7 +547,7 @@ def new_styles(self, styles):
  self.style_listener(styles)
 
 
-def init_curses(fd):
+def init_curses(fd=sys.__stderr__):
  try:
  import curses