[trivial][merge] unbreak benchmarks

[Ian Clatworthy]

Martin Pool wrote:
> This code depended on some other modules already being loaded, and
> breaks the benchmarks in bzr.dev:
>
selftest --benchmark crashes out in 0.15 btw. It might be the same 
issue? I found that yesterday but hadn't reported it because I hadn't 
got around to verifying whether it was still a problem in bzr.dev or 
not. I do know that it failed regardless of whether --cache-dir was 
specified or not.

Some other related stuff I'm yet to raise bugs for:

* "selftest --benchmark --cache-dir xxx" expects xxx to exist when my 
expectation was that it would be created if it didn't exist

* the benchdisplay plug-in fails to load in 0.15 for me. Maybe I don't 
have PIL or something else installed? Either way, the error message is 
very uninformative: just "Failed to load plug-in".

If anyone knows what the issues are abve off the top of their head, 
please let me know. Otherwise, I'll dig a bit deeper and raise the 
relevant bugs in the Launchpad tracker.

Ian C.