wireprotov1server: capture Abort type before accessing the `hint` attribute

Although the previous code worked, pytypes complained because `exc` is caught
above as `BundleValueError, Abort, PushRaced`, and the other two don't have this
attribute.

Differential Revision: https://phab.mercurial-scm.org/D7463

mercurial/wireprotov1server.py

@@ -679,7 +679,7 b' def unbundle(repo, proto, heads):'
             if not getattr(exc, 'duringunbundle2', False):
                 try:
                     raise
-                except error.Abort:
+                except error.Abort as exc:
                     # The old code we moved used procutil.stderr directly.
                     # We did not change it to minimise code change.
                     # This need to be moved to something proper.