Array allocation failure about pyopencl

[inducer]

cc @alexfikl (since this came from a change you made)

[kif]

To reproduce the bug:

In [1]: import pyopencl, pyopencl.array, numpy
In [2]: ctx = pyopencl.create_some_context()
In [3]: queue = pyopencl.CommandQueue(ctx)
In [4]: ary = pyopencl.array.empty(queue, numpy.uint64(10), dtype="float32")
In [5]: ary = pyopencl.array.empty(queue, (numpy.uint64(10),), dtype="float32")
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-1e5620a87523> in <module>
----> 1 ary = pyopencl.array.empty(queue, (numpy.uint64(10),), dtype="float32")

/usr/lib/python3/dist-packages/pyopencl/array.py in __init__(***failed resolving arguments***)
    532                         context = queue.context
    533 
--> 534                     self.base_data = cl.Buffer(
    535                             context, cl.mem_flags.READ_WRITE, alloc_nbytes)
    536                 else:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. pyopencl._cl.Buffer(context: pyopencl._cl.Context, flags: int, size: int = 0, hostbuf: object = None)

Invoked with: <pyopencl.Context at 0x1040dd0 on <pyopencl.Device 'gfx900:xnack-' on 'AMD Accelerated Parallel Processing' at 0x1d34a20>>, 1, 40.0