xenvm lvextend command error message not clear enough

[cheng-z]

Run lvextend to extend the size of the logic volume to exceed the available space, the error message will git as:
Xenvm_interface.Internal_error("Failure("Only this much space is available: 2035")")

It should have a unit of MB or GB or something to show a understandable value.

[djs55]

For reference the normal LVM commands have:

$ sudo lvextend packer-virtualbox-iso-vg/swap_1 -L 1T
  Extending logical volume swap_1 to 1.00 TiB  [ on stdout ]
  Insufficient free space: 262016 extents needed, but only 0 available  [ on stderr ]

$ echo $?
5

[djs55]

And normal lvcreate has:

$ sudo lvcreate packer-virtualbox-iso-vg -n test -L 1T
  Volume group "packer-virtualbox-iso-vg" has insufficient free space (0 extents): 262144 required.

$ echo $?
5