Many thanks to Brandon Bocklund and Richard Otis for investigating this. Progress is being made on master but I think we have also reached the conclusion that no fix is needed in 1.9 here.
There was a problem with the release scripts that I fixed here:
From there I think we're good to go so I expect to release sympy 1.9 ASAP.
It's bedtime here though and I'll be busy tomorrow so the release will not happen immediately.
Oscar