'nova-manage floating create' does nothing for /31 or /32 address range

Version: 2012.1-LOCALBRANCH:LOCALREVISION (from the ubuntu 2012.1-0ubuntu2 packages, i.e. essex/stable).

'nova-manage floating create' silently does nothing if you pass a /31 or /32 address range. E.g.

# nova-manage floating list
No floating IP addresses have been defined.
# nova-manage floating create 10.20.223.242/31

No error was reported, so my expectation is that this has added 2 IP addresses to the pool, but:

# nova-manage floating list
No floating IP addresses have been defined.

The same occurs for a /32 network:

# nova-manage floating create 10.20.223.242/32
# nova-manage floating list
No floating IP addresses have been defined.

This occurs because nova/bin/nova-manage:FloatingIpCommands address_to_hosts calls netaddr.IPNetwork.iter_hosts, which states that "Any subnet that contains less than 4 IP addresses yields an empty list" (<http://packages.python.org/netaddr/netaddr.ip.IPNetwork-class.html#iter_hosts>):

>>> list(netaddr.IPNetwork('10.20.223.242/31').iter_hosts())
[]

I believe the netaddr.IPNetwork.iter_hosts behaviour is reasonable, as once the network and broadcast addresses are excluded, no addresses remain in an /31 network. But rather than silently doing nothing in such cases, nova-manage should report an error and suggest to the user that they add the IP addresses individually (which does work).