Pool.create source_volume argument is optional

qubes/storage/__init__.py

@@ -251,7 +251,7 @@ class Pool(object):
     def __xml__(self):
         return lxml.etree.Element('pool', **self.config)
 
-    def create(self, volume, source_volume):
+    def create(self, volume, source_volume=None):
         ''' Create the given volume on disk or copy from provided
             `source_volume`.
         '''

qubes/storage/kernels.py

@@ -67,7 +67,7 @@ class LinuxKernel(Pool):
     def clone(self, source, target):
         return target
 
-    def create(self, volume, source_volume):
+    def create(self, volume, source_volume=None):
         return volume
 
     def commit_template_changes(self, volume):