Fix missing import in wavelet_wrappers

[joezuntz]

This is a pretty trivial change to fix a crash in the logging mechanism.

[jasonmcewen]

Thanks @joezuntz. We'll merge shortly.

@joezuntz Would it be useful to have this on PyPi straight away or should we just include when we do a next release?

@CosmoMatt We don't have a next release planned soon so perhaps we should just push to PyPi now? Unless you think you might uncover other small updates like this @joezuntz?

[joezuntz]

This can definitely wait for the next release for what I'm doing - it's a trivial manual fix on my laptop for testing and on NERSC I'll use larger area maps (so can usefully test with lower bandwidth) anyway.