skip vectorized staggered RNG test if islpy not available

pystencils_tests/test_random.py

@@ -173,6 +173,7 @@ def test_staggered(vectorized):
         return
     if not get_supported_instruction_sets():
         pytest.skip("cannot detect CPU instruction set")
+    pytest.importorskip('islpy')
     cpu_vectorize_info = {'assume_inner_stride_one': True, 'assume_aligned': False,
                           'instruction_set': get_supported_instruction_sets()[0]}