fix tests

packages/py-viziphant/package.py

@@ -30,11 +30,13 @@ class PyViziphant(PythonPackage):
     depends_on('py-seaborn@0.9.0:', type=('build', 'run'))
 
     depends_on("py-pytest", type=("test"), when="@0.3.0:")
-    depends_on("py-elephant@0.9.0 +extras", type=("test"), when="@0.3.0:")
+    depends_on("py-elephant@0.9.0:+extras", type=("test"), when="@0.3.0:")
 
     @run_after('install')
     @on_package_attributes(run_tests=True)
     def install_test(self):
         # run tests
-        pytest = which('pytest')
-        pytest()
+        # TODO: replace if clause with @run_after('install', when='@0.3.0:') after update to Spack v0.19
+        if self.spec.version >= Version('0.3.0'):
+            pytest = which('pytest')
+            pytest()