keepalive: remove useless parentheses around exception type

mercurial/keepalive.py

@@ -345,7 +345,7 b' class KeepAliveHandler(object):'
                     h.putheader('Content-length', '%d' % len(data))
             else:
                 h.putrequest('GET', req.get_selector(), **skipheaders)
-        except (socket.error) as err:
+        except socket.error as err:
             raise urllib2.URLError(err)
         for k, v in headers.items():
             h.putheader(k, v)