yes, I worked that out eventually and I did indeed got past that error by turning default on at the command line.
However, now I have a new error as well as an old one:
I totally reinstalled Debian wheezy, to have a known starting point. I then installed KVM using the exact steps listed at https://www.whonix.org/wiki/KVM including checking the versions of the installed KVM packages.
I then took an image backup of the computer to be able to return to if I should happen to trash the setup.
I also noticed that the filenames of the qcow2 files in the xml files are incorrect. they are something like Whonix-gateway.qcow2 while the actual files are something like Whonix-Gateway-9.3 so I amended those entries. I hadn't been looking at the xml files because editing them is listed as an optional step.
I then went through the import steps (after turning on default) and, when I ran the gateway vm from virt-manager, I received the following error:
Error starting domain: internal error hugetlbfs filesystem is not mounted
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 45, in cb_wrapper
callback(asyncjob, *args, **kwargs)
File "/usr/share/virt-manager/virtManager/asyncjob.py", line 66, in tmpcb
File "/usr/share/virt-manager/virtManager/domain.py", line 1114, in startup
File "/usr/lib/python2.7/dist-packages/libvirt.py", line 620, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error hugetlbfs filesystem is not mounted
I note also that, in virt-manager, the virtual network "Whonix" has on its properties pane: "Error selecting network: Unsupported data type: " which is the same error as previously mentioned (but after I have restored this computer from the image backup).
By the way, the way I have been putting the files in the Images directory is by copying the xz files into that directory and then running tar -xvf on them there. That should preserve their sparseness. Of course, I also adjusted the paths appropriately in the import commands. I had no errors when running those import commands.
I would appreciate any input on this!