Issue937: error messages from hooks not sent over HTTP.

Turns out that stderr - where ui.warn would send messages - was not
being proxied over the HTTP connection. stdout was, and it seems you
need both. (The streams are interleaved for readability.)

Tested on Ubuntu 7.10 with lighttpd on hgweb.cgi with HTTP Basic auth,
no SSL, using a changeset failing win32text.forbidcrlf.

mercurial/hgweb/protocol.py

@@ -175,8 +175,8 b' def unbundle(web, req):'
 
                 # send addchangegroup output to client
 
-                old_stdout = sys.stdout
-                sys.stdout = cStringIO.StringIO()
+                oldio = sys.stdout, sys.stderr
+                sys.stderr = sys.stdout = cStringIO.StringIO()
 
                 try:
                     url = 'remote:%s:%s' % (proto,
@@ -188,7 +188,7 b' def unbundle(web, req):'
                         ret = 0
                 finally:
                     val = sys.stdout.getvalue()
-                    sys.stdout = old_stdout
+                    sys.stdout, sys.stderr = oldio
                 req.write('%d\n' % ret)
                 req.write(val)
             finally: