sudo ubuntu-vm-builder kvm trusty fails

The command

sudo ubuntu-vm-builder kvm trusty fails

fails with these errors:

Traceback (most recent call last):
  File "/usr/bin/ubuntu-vm-builder", line 24, in <module>
    uvb.main()
  File "/usr/lib/python2.7/dist-packages/VMBuilder/contrib/cli.py", line 228, in main
    hypervisor.install_os()
  File "/usr/lib/python2.7/dist-packages/VMBuilder/hypervisor.py", line 70, in install_os
    self.call_hooks('install_kernel', self.chroot_dir)
  File "/usr/lib/python2.7/dist-packages/VMBuilder/distro.py", line 67, in call_hooks
    call_hooks(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/VMBuilder/util.py", line 159, in call_hooks
    getattr(plugin, func)(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/VMBuilder/plugins/ubuntu/distro.py", line 190, in install_kernel
    self.suite.install_kernel(destdir)
  File "/usr/lib/python2.7/dist-packages/VMBuilder/plugins/ubuntu/dapper.py", line 307, in install_kernel
    run_cmd('chroot', destdir, 'apt-get', '--force-yes', '-y', 'install', self.kernel_name(), env={ 'DEBIAN_FRONTEND' : 'noninteractive' })
  File "/usr/lib/python2.7/dist-packages/VMBuilder/util.py", line 120, in run_cmd
    raise VMBuilderException, "Process (%s) returned %d. stdout: %s, stderr: %s" % (args.__repr__(), status, mystdout.buf, mystderr.buf)
VMBuilder.exception.VMBuilderException: Process (['chroot', '/tmp/tmprm0Zzl', 'apt-get', '--force-yes', '-y', 'install', 'linux-image-virtual']) returned 100. stdout: Reading package lists...

also it looks like the machine creation process is just interrupted after this error and it seems to leave a lot of files in tmp without cleaning up. It would be much better to have some kind of exception handling that does clean up after a fail.