bundle2: include stderr when capturing handlers output

We do not discriminate between stdout and stderr yet. But this will do for now.

mercurial/bundle2.py

@@ -309,7 +309,7 b' def processbundle(repo, unbundler, trans'
             # itself represents a defect of a different variety).
             output = None
             if op.reply is not None:
-                op.ui.pushbuffer()
+                op.ui.pushbuffer(error=True)
                 output = ''
             try:
                 handler(op, part)

tests/test-bundle2.t

@@ -37,6 +37,7 b' Create an extension to test bundle2 API'
   > def pinghandler(op, part):
   >     op.ui.write('received ping request (id %i)\n' % part.id)
   >     if op.reply is not None:
+  >         op.ui.write_err('replying to ping request (id %i)\n' % part.id)
   >         rpart = bundle2.bundlepart('test:pong',
   >                                    [('in-reply-to', str(part.id))])
   >         op.reply.addpart(rpart)
@@ -509,7 +510,8 b' The reply is a bundle'
       Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
       Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
       Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
-  \x00\x00\x00\x00\x00\x1e	test:pong\x00\x00\x00\x01\x01\x00\x0b\x01in-reply-to5\x00\x00\x00\x00\x00\x1b\x06output\x00\x00\x00\x02\x00\x01\x0b\x01in-reply-to5\x00\x00\x00\x1dreceived ping request (id 5) (esc)
+  \x00\x00\x00\x00\x00\x1e	test:pong\x00\x00\x00\x01\x01\x00\x0b\x01in-reply-to5\x00\x00\x00\x00\x00\x1b\x06output\x00\x00\x00\x02\x00\x01\x0b\x01in-reply-to5\x00\x00\x00=received ping request (id 5) (esc)
+  replying to ping request (id 5)
   \x00\x00\x00\x00\x00\x00 (no-eol) (esc)
 
 The reply is valid
@@ -527,7 +529,7 b' The reply is valid'
     :output:
       mandatory: 0
       advisory: 1
-      payload: 29 bytes
+      payload: 61 bytes
   parts count:   3
 
 Unbundle the reply to get the output:
@@ -538,6 +540,7 b' Unbundle the reply to get the output:'
   remote:     Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
   remote:     Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
   remote: received ping request (id 5)
+  remote: replying to ping request (id 5)
   0 unread bytes
 
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