Fix varlen tests on older NumPy versions.

Older NumPy versions don't respect NPY_ENSURECOPY in some
circumstances, which means that the data in the varlen result
array is no longer valid after the underlying buffer is freed.

tiledb/libtiledb.pyx

@@ -3823,11 +3823,11 @@ cdef class Array(object):
                 # note: must not divide by itemsize for a string, because it may be zero (e.g 'S0')
                 dims[0] = el_bytelen / el_dtype.base.itemsize
                 newobj = \
-                    PyArray_NewFromDescr(
+                    np.copy(PyArray_NewFromDescr(
                         <PyTypeObject*> np.ndarray,
                         el_dtype.base, 1, dims, NULL,
                         el_ptr,
-                        np.NPY_ENSURECOPY, <object> NULL)
+                        0, <object> NULL))
 
             # set the output object
             out_flat[el] = newobj

tiledb/tests/test_libtiledb.py

@@ -1046,14 +1046,13 @@ def test_varlen_write_floats(self):
         att = tiledb.Attr(dtype=np.float64, var=True, ctx=ctx)
 
         schema = tiledb.ArraySchema(dom, (att,), ctx=ctx)
-
         tiledb.DenseArray.create(self.path("foo"), schema)
         with tiledb.DenseArray(self.path("foo"), mode='w', ctx=ctx) as T:
             T[:] = A
 
         with tiledb.DenseArray(self.path("foo"), mode='r', ctx=ctx) as T:
             T_ = T[:]
-            self.assertEqual(len(A), len(T))
+            self.assertEqual(len(A), len(T_))
             # can't use assert_array_equal w/ np.object array
             self.assertTrue(all(np.array_equal(x,A[i]) for i,x in enumerate(T_)))