Martin von Zweigbergk <martinvonz@google.com> [Fri, 25 Mar 2016 23:05:32 -0700] rev 28669
bundle: avoid crash when no good changegroup version found
When using treemanifests, only changegroup3 bundles can be
created. However, there is currently no way of requesting a
changegroup3 bundle, so we run into an assertion in
changegroup.getbundler() when trying to get a changroup2
bundler. Let's avoid the traceback and print a short error message
instead.