pager: check if signal.SIGPIPE exists

We have to check for signal.SIGPIPE before we attempt
to set it.

hgext/pager.py

@@ -1,103 +1,101 b''
 # pager.py - display output using a pager
 #
 # Copyright 2008 David Soria Parra <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # To load the extension, add it to your configuration file:
 #
 #   [extension]
 #   pager =
 #
 # Run "hg help pager" to get info on configuration.
 
 '''browse command output with an external pager
 
 To set the pager that should be used, set the application variable::
 
   [pager]
   pager = less -FRSX
 
 If no pager is set, the pager extensions uses the environment variable
 $PAGER. If neither pager.pager, nor $PAGER is set, no pager is used.
 
 You can disable the pager for certain commands by adding them to the
 pager.ignore list::
 
   [pager]
   ignore = version, help, update
 
 You can also enable the pager only for certain commands using
 pager.attend. Below is the default list of commands to be paged::
 
   [pager]
   attend = annotate, cat, diff, export, glog, log, qdiff
 
 Setting pager.attend to an empty value will cause all commands to be
 paged.
 
 If pager.attend is present, pager.ignore will be ignored.
 
 To ignore global commands like :hg:`version` or :hg:`help`, you have
 to specify them in your user configuration file.
 
 The --pager=... option can also be used to control when the pager is
 used. Use a boolean value like yes, no, on, off, or use auto for
 normal behavior.
 '''
 
 import atexit, sys, os, signal, subprocess
 from mercurial import commands, dispatch, util, extensions
 from mercurial.i18n import _
 
 def _runpager(p):
     pager = subprocess.Popen(p, shell=True, bufsize=-1,
                              close_fds=util.closefds, stdin=subprocess.PIPE,
                              stdout=sys.stdout, stderr=sys.stderr)
 
     stdout = os.dup(sys.stdout.fileno())
     stderr = os.dup(sys.stderr.fileno())
     os.dup2(pager.stdin.fileno(), sys.stdout.fileno())
     if util.isatty(sys.stderr):
         os.dup2(pager.stdin.fileno(), sys.stderr.fileno())
 
     @atexit.register
     def killpager():
         pager.stdin.close()
         os.dup2(stdout, sys.stdout.fileno())
         os.dup2(stderr, sys.stderr.fileno())
         pager.wait()
 
 def uisetup(ui):
     if ui.plain() or '--debugger' in sys.argv or not util.isatty(sys.stdout):
         return
 
     def pagecmd(orig, ui, options, cmd, cmdfunc):
         p = ui.config("pager", "pager", os.environ.get("PAGER"))
 
         if p:
             attend = ui.configlist('pager', 'attend', attended)
             auto = options['pager'] == 'auto'
             always = util.parsebool(options['pager'])
             if (always or auto and
                 (cmd in attend or
                  (cmd not in ui.configlist('pager', 'ignore') and not attend))):
                 ui.setconfig('ui', 'formatted', ui.formatted())
                 ui.setconfig('ui', 'interactive', False)
-                try:
+                if util.safehasattr(signal, "SIGPIPE"):
                     signal.signal(signal.SIGPIPE, signal.SIG_DFL)
-                except ValueError:
-                    pass
                 _runpager(p)
         return orig(ui, options, cmd, cmdfunc)
 
     extensions.wrapfunction(dispatch, '_runcommand', pagecmd)
 
 def extsetup(ui):
     commands.globalopts.append(
         ('', 'pager', 'auto',
          _("when to paginate (boolean, always, auto, or never)"),
          _('TYPE')))
 
 attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']