Raise at least one error for parallel tests.
Raise at least one error for parallel tests.

Ideally, we should grab all exceptions raised and let the user see them.  For
now, at least make sure that the primary test passes.

paalge/scikit-image,vighneshbirodkar/scikit-image,rjeli/scikit-image,Hiyorimi/scikit-image,paalge/scikit-image,ofgulban/scikit-image,vighneshbirodkar/scikit-image,Hiyorimi/scikit-image,ajaybhat/scikit-image,pratapvardhan/scikit-image,pratapvardhan/scikit-image,ajaybhat/scikit-image,paalge/scikit-image,rjeli/scikit-image,ofgulban/scikit-image,ofgulban/scikit-image,vighneshbirodkar/scikit-image,rjeli/scikit-image