scmposix: don't subscript IOError

This warning disabling has been in place since late 2019 in 667f56d73ceb.  We
should have had some py3 support at the time, but both pytype complains and
subscripting a real FileNotFoundError generated in `hg debugshell` crashed, so
maybe this fixes a problem.  It looks like all other instances of subscripting
exceptions have been replaced (at least as far as greping for `== errno.`
revealed).

mercurial/scmposix.py

@@ -1,95 +1,95 b''
 import array
 import errno
 import fcntl
 import os
 import sys
 
 from .pycompat import getattr
 from . import (
     encoding,
     pycompat,
     util,
 )
 
 # BSD 'more' escapes ANSI color sequences by default. This can be disabled by
 # $MORE variable, but there's no compatible option with Linux 'more'. Given
 # OS X is widely used and most modern Unix systems would have 'less', setting
 # 'less' as the default seems reasonable.
 fallbackpager = b'less'
 
 
 def _rcfiles(path):
     rcs = [os.path.join(path, b'hgrc')]
     rcdir = os.path.join(path, b'hgrc.d')
     try:
         rcs.extend(
             [
                 os.path.join(rcdir, f)
                 for f, kind in sorted(util.listdir(rcdir))
                 if f.endswith(b".rc")
             ]
         )
     except OSError:
         pass
     return rcs
 
 
 def systemrcpath():
     path = []
     if pycompat.sysplatform == b'plan9':
         root = b'lib/mercurial'
     else:
         root = b'etc/mercurial'
     # old mod_python does not set sys.argv
     if len(getattr(sys, 'argv', [])) > 0:
         p = os.path.dirname(os.path.dirname(pycompat.sysargv[0]))
         if p != b'/':
             path.extend(_rcfiles(os.path.join(p, root)))
     path.extend(_rcfiles(b'/' + root))
     return path
 
 
 def userrcpath():
     if pycompat.sysplatform == b'plan9':
         return [encoding.environ[b'home'] + b'/lib/hgrc']
     elif pycompat.isdarwin:
         return [os.path.expanduser(b'~/.hgrc')]
     else:
         confighome = encoding.environ.get(b'XDG_CONFIG_HOME')
         if confighome is None or not os.path.isabs(confighome):
             confighome = os.path.expanduser(b'~/.config')
 
         return [
             os.path.expanduser(b'~/.hgrc'),
             os.path.join(confighome, b'hg', b'hgrc'),
         ]
 
 
 def termsize(ui):
     try:
         import termios
 
         TIOCGWINSZ = termios.TIOCGWINSZ  # unavailable on IRIX (issue3449)
     except (AttributeError, ImportError):
         return 80, 24
 
     for dev in (ui.ferr, ui.fout, ui.fin):
         try:
             try:
                 fd = dev.fileno()
             except AttributeError:
                 continue
             if not os.isatty(fd):
                 continue
             arri = fcntl.ioctl(fd, TIOCGWINSZ, b'\0' * 8)
             height, width = array.array('h', arri)[:2]
             if width > 0 and height > 0:
                 return width, height
         except ValueError:
             pass
         except IOError as e:
-            if e[0] == errno.EINVAL:  # pytype: disable=unsupported-operands
+            if e.errno == errno.EINVAL:
                 pass
             else:
                 raise
     return 80, 24