Fix assertion of pairwise potential shape, thx @Pandoro.
Fix assertion of pairwise potential shape, thx @Pandoro.

crowd-ai/post-processing-experiments,lucasb-eyer/pydensecrf,crowd-ai/post-processing-experiments,crowd-ai/post-processing-experiments,lucasb-eyer/pydensecrf,crowd-ai/post-processing-experiments,lucasb-eyer/pydensecrf