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.

Ancestors of 5
4 2 0 
Ancestors of 6 and 5
3 4 2 1 0 
Ancestors of 5 and 4
4 2 0 
Ancestors of 7, stop at 6
6 
Ancestors of 7, including revs
7 6 5 3 4 2 1 0 
Ancestors of 7, 5 and 3, including revs
7 5 3 6 4 2 1 0 

Descendants of 5
7 8 
Descendants of 5 and 3
6 7 8 
Descendants of 5 and 4
5 7 8