Fix flake8 fails
Fix flake8 fails

- Remove unused import of platform
- Remove try / except from open_cudalib - the error was in using a
  bare except - rather than making it more specific, the try /
  except is simply removed, as CDLL will raise an OSError itself
  if the library is not found.

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