hook: ignore EPIPE when flushing stdout/stderr

This fixes the bug described in the parent commit.
test-transaction-rollback-on-sigpipe.t is updated to show the new
behavior.

Differential Revision: https://phab.mercurial-scm.org/D9152

mercurial/hook.py

@@ -8,6 +8,7 b''
 from __future__ import absolute_import
 
 import contextlib
+import errno
 import os
 import sys
 
@@ -289,10 +290,18 b' def redirect_stdio():'
         # The stderr is fully buffered on Windows when connected to a pipe.
         # A forcible flush is required to make small stderr data in the
         # remote side available to the client immediately.
+        try:
         procutil.stderr.flush()
+        except IOError as err:
+            if err.errno not in (errno.EPIPE, errno.EIO, errno.EBADF):
+                raise error.StdioError(err)
 
         if _redirect and oldstdout >= 0:
+            try:
             procutil.stdout.flush()  # write hook output to stderr fd
+            except IOError as err:
+                if err.errno not in (errno.EPIPE, errno.EIO, errno.EBADF):
+                    raise error.StdioError(err)
             os.dup2(oldstdout, stdoutno)
             os.close(oldstdout)
 

tests/test-transaction-rollback-on-sigpipe.t

@@ -64,4 +64,4 b' disconnecting. Then exit nonzero, to for'
   abort: stream ended unexpectedly (got 0 bytes, expected 4)
 
   $ check_for_abandoned_transaction
-  Abandoned transaction!
+  [1]