Non existing iid (#124)

* non-existing-uid

* legal iid comment

Author: avishalom

integration/test_instance_id.py

@@ -20,5 +20,6 @@
 
 def test_delete_non_existing():
     with pytest.raises(instance_id.ApiCallError) as excinfo:
-        instance_id.delete_instance_id('non-existing')
-    assert str(excinfo.value) == 'Instance ID "non-existing": Failed to find the instance ID.'
+        # legal instance IDs are /[cdef][A-Za-z0-9_-]{9}[AEIMQUYcgkosw048]/
+        instance_id.delete_instance_id('fictive-ID0')
+    assert str(excinfo.value) == 'Instance ID "fictive-ID0": Failed to find the instance ID.'