[PATCH 1 of 3 STABLE] exchange: fix invalid reference to bundle2.UnknownPartError caught by pyflakes

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1398742502 -32400
#      Tue Apr 29 12:35:02 2014 +0900
# Branch stable
# Node ID 0b3e8b75ec319048a8ae6ade1340124598cd573d
# Parent  920b654c7a16fc208fe62ca58609434ef34a0247
exchange: fix invalid reference to bundle2.UnknownPartError caught by pyflakes

diff --git a/mercurial/exchange.py b/mercurial/exchange.py
--- a/mercurial/exchange.py
+++ b/mercurial/exchange.py
@@ -587,7 +587,7 @@ def _pullbundle2(pullop):
     bundle = pullop.remote.getbundle('pull', **kwargs)
     try:
         op = bundle2.processbundle(pullop.repo, bundle, pullop.gettransaction)
-    except UnknownPartError, exc:
+    except bundle2.UnknownPartError, exc:
         raise util.Abort('missing support for %s' % exc)
     assert len(op.records['changegroup']) == 1
     pullop.cgresult = op.records['changegroup'][0]['return']