Fix issue with test discovery and broken CUDA drivers.
Fix issue with test discovery and broken CUDA drivers.

This patch allows the test discovery mechanism to work even in the
case of a broken/misconfigured CUDA driver.

Fixes #2841

cpcloud/numba,gmarkall/numba,cpcloud/numba,numba/numba,seibert/numba,numba/numba,sklam/numba,stuartarchibald/numba,stuartarchibald/numba,stonebig/numba,sklam/numba,stonebig/numba,stuartarchibald/numba,numba/numba,seibert/numba,sklam/numba,gmarkall/numba,jriehl/numba,numba/numba,gmarkall/numba,jriehl/numba,seibert/numba,cpcloud/numba,stonebig/numba,stonebig/numba,stuartarchibald/numba,sklam/numba,stonebig/numba,gmarkall/numba,stuartarchibald/numba,IntelLabs/numba,IntelLabs/numba,jriehl/numba,numba/numba,jriehl/numba,seibert/numba,sklam/numba,cpcloud/numba,IntelLabs/numba,jriehl/numba,IntelLabs/numba,cpcloud/numba,gmarkall/numba,seibert/numba,IntelLabs/numba