sshpeer: break "OutOfBandError" feature for ssh (BC)

sshpeer: break "OutOfBandError" feature for ssh (BC)

When we'll be using the ssh's 'stderr' for realtime output successfully, it will
no longer be possible to use 'stderr' to carry the error message (because it
is already consumed by the real time output logic.

This feature is very rarely used (test says largefile only) and I think
breaking its output pattern is worth the benefit of having real time output with
ssh.

--- a/mercurial/sshpeer.py	Wed May 20 18:17:40 2015 -0500
+++ b/mercurial/sshpeer.py	Wed May 20 12:33:12 2015 -0500
@@ -195,16 +195,9 @@
     def _recv(self):
         l = self.pipei.readline()
         if l == '\n':
-            err = []
-            while True:
-                line = self.pipee.readline()
-                if line == '-\n':
-                    break
-                err.extend([line])
-            if len(err) > 0:
-                # strip the trailing newline added to the last line server-side
-                err[-1] = err[-1][:-1]
-            self._abort(error.OutOfBandError(*err))
+            self.readerr()
+            msg = _('check previous remote output')
+            self._abort(error.OutOfBandError(hint=msg))
         self.readerr()
         try:
             l = int(l)

--- a/tests/test-largefiles-wireproto.t	Wed May 20 18:17:40 2015 -0500
+++ b/tests/test-largefiles-wireproto.t	Wed May 20 12:33:12 2015 -0500
@@ -111,11 +111,14 @@
 
 vanilla clients locked out from largefiles ssh repos
   $ hg --config extensions.largefiles=! clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/r4 r5
-  abort: remote error:
-  
-  This repository uses the largefiles extension.
-  
-  Please enable it in your Mercurial config file.
+  remote: 
+  remote: This repository uses the largefiles extension.
+  remote: 
+  remote: Please enable it in your Mercurial config file.
+  remote: 
+  remote: -
+  abort: remote error
+  (check previous remote output)
   [255]
 
 #if serve