Add test guards

Change-Id: I1d7633e20daab33642fa5c4a12e474a4def4d8b8

Author: mbaret

tests/python/contrib/test_ethosu/cascader/test_propagator.py

@@ -14,10 +14,12 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-from tvm.contrib.ethosu.cascader import StripeConfig, Propagator
-
 import pytest
+
+pytest.importorskip("ethosu.vela")
+
 from math import isclose
+from tvm.contrib.ethosu.cascader import StripeConfig, Propagator
 
 
 def test_propagator():

tests/python/contrib/test_ethosu/cascader/test_stripe_config.py

@@ -14,10 +14,12 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
-from tvm.contrib.ethosu.cascader.stripe_config import StripeConfig, count_stripes
-
 import pytest
 
+pytest.importorskip("ethosu.vela")
+
+from tvm.contrib.ethosu.cascader.stripe_config import StripeConfig, count_stripes
+
 
 def test_stripe_config():
     shape = [1, 2, 3]