bundle1: display server abort hint during unbundle

The code was printing the abort message but not the hint. This is now fixed.

mercurial/wireproto.py

@@ -981,6 +981,8 b' def unbundle(repo, proto, heads):'
                 # This need to be moved to something proper.
                 # Feel free to do it.
                 util.stderr.write("abort: %s\n" % exc)
+                if exc.hint is not None:
+                    util.stderr.write("(%s)\n" % exc.hint)
                 return pushres(0)
             except error.PushRaced:
                 return pusherr(str(exc))

tests/test-bundle2-exchange.t

@@ -1113,6 +1113,7 b' Verify bundle1 pushes can be disabled'
   pushing to ssh://user@dummy/bundle2onlyserver
   searching for changes
   remote: abort: incompatible Mercurial client; bundle2 required
+  remote: (see https://www.mercurial-scm.org/wiki/IncompatibleClient)
   [1]
 
   $ hg push