In discovery, treat suite import failure similarly as build failure
In discovery, treat suite import failure similarly as build failure

Instead of giving up benchmark discovery on import failure, treat it
similarly as build failures.

Also try branch commits immediately if the first user-provided benchmark
commit fails to work, and try rest of the commits only after those.

airspeed-velocity/asv,airspeed-velocity/asv,spacetelescope/asv,airspeed-velocity/asv,spacetelescope/asv,qwhelan/asv,spacetelescope/asv,qwhelan/asv,qwhelan/asv,airspeed-velocity/asv,qwhelan/asv,spacetelescope/asv