HEAD breaks testdrive -u ./foo.iso

kirkland@x200:/local/virt/iso$ testdrive -u lucid-desktop-amd64.iso
INFO: version passed: False

INFO: config passed: None

INFO: Trying config in /etc/testdriverc

INFO: Using configuration in /etc/testdriverc

INFO: Trying config in /home/kirkland/.testdriverc

INFO: Trying config in /home/kirkland/.config/testdrive/testdriverc

INFO: Using KVM for virtual machine hosting...

INFO: Retrieving Ubuntu Development Release codename from cache...

INFO: Syncing the specified ISO...

      file://lucid-desktop-amd64.iso

Traceback (most recent call last):
  File "/usr/bin/testdrive", line 368, in <module>
    main()
  File "/usr/bin/testdrive", line 334, in main
    run_or_die(cmd)
  File "/usr/bin/testdrive", line 85, in run_or_die
    if run(cmd) != 0:
  File "/usr/bin/testdrive", line 82, in run
    return(os.system(cmd))
TypeError: system() argument 1 must be string, not None

This looks wrong:

        info("Syncing the specified ISO...")
        print(" %s" % td.ISO_URL)
        cmd = td.get_proto()
        print(cmd)
        if cmd == 0:
                error("ISO not found at [%s]" % td.ISO_URL)
        elif cmd == 1:
                error("Unsupported protocol [%s]" % td.PROTO)
        run_or_die(cmd)