harness: Default to an empty list, not None.

Signed-off-by: David Cock <david.cock@inf.ethz.ch>

diff --git a/tools/harness/machines/__init__.py b/tools/harness/machines/__init__.py
index 779f9a7..d174096 100644 (file)
--- a/tools/harness/machines/__init__.py
+++ b/tools/harness/machines/__init__.py
@@ -46,11 +46,11 @@ class Machine(object):
 
     def get_kernel_args(self):
         """Returns list of machine-specific arguments to add to the kernel command-line"""
-        return None
+        return []
 
     def get_pci_args(self):
         """Returns list of machine-specific arguments to add to the PCI command-line"""
-        return None
+        return []
 
     def get_boot_timeout(self):
         """Returns a machine-specific timeout (in seconds), or None for the default"""