Error message trying to reserve an IP address when no static range is defined is misleading

To reproduce:

 1). Create a cluster with a managed interface, and set the dynamic range to 10.0.0.2 - 10.0.0.128 (or equivalent for your network). Leave the static range blank.
 2). Run `maas <profile> ipaddresses reserve network=<network CIDR> requested_address=<some address on the network>

You'll end up with something like:

graham@dodger:~⟫ maas maas ipaddresses reserve network=10.0.0.0/16 requested_address=10.0.0.100
No network found matching 10.0.0.0/16

Now, clearly the network exists, it's just that you haven't defined a static range. The error message makes no hint at this, though.