ignore EPIPE in ui.err_write

It avoids not being able to abort a transaction when a push via ssh fails.
Maybe some other place should ignore EPIPE too.

mercurial/ui.py

@@ -8,7 +8,7 b''
 import ConfigParser
 from i18n import gettext as _
 from demandload import *
-demandload(globals(), "os re socket sys util tempfile")
+demandload(globals(), "errno os re socket sys tempfile util")
 
 class ui(object):
     def __init__(self, verbose=False, debug=False, quiet=False,
@@ -179,9 +179,13 b' class ui(object):'
             sys.stdout.write(str(a))
 
     def write_err(self, *args):
+        try:
         if not sys.stdout.closed: sys.stdout.flush()
         for a in args:
             sys.stderr.write(str(a))
+        except IOError, inst:
+            if inst.errno != errno.EPIPE:
+                raise
 
     def flush(self):
         try: