Add a missed except * (#1057)

Authors:
  - Ashwin Srinath (https://github.com/shwina)

Approvers:
  - Mark Harris (https://github.com/harrism)
  - Bradley Dice (https://github.com/bdice)
  - https://github.com/jakirkham

URL: #1057

python/rmm/_lib/device_buffer.pyx

@@ -344,7 +344,7 @@ cdef void _copy_async(const void* src,
                       void* dst,
                       size_t count,
                       ccudart.cudaMemcpyKind kind,
-                      cuda_stream_view stream) nogil:
+                      cuda_stream_view stream) nogil except *:
     """
     Asynchronously copy data between host and/or device pointers