flannel doesn't error early enough when configured with a bad subnet

[tomdee]

Seen on flannel v0.7.1

Using this config:

➜  ~ etcdctl set /coreos.com/network/config '{
                                          "Network": "10.0.0.0/32",
                                          "Backend": {
                                            "Type": "alloc"          
                                          }
                                        }'

I see

I0427 16:38:16.995413    9492 main.go:241] Found network config - Backend type: alloc
I0427 16:38:17.002158    9492 local_manager.go:181] Picking subnet in range 10.0.0.0 ... 10.0.0.1
I0427 16:38:17.003740    9492 local_manager.go:167] Allocated lease (10.0.0.0/33) to current node (192.168.10.218) 
I0427 16:38:17.003949    9492 main.go:196] Wrote subnet file to /run/flannel/subnet.env
I0427 16:38:17.003975    9492 main.go:201] Finished starting backend.
E0427 16:38:17.008344    9492 watch.go:171] Subnet watch failed: failed to parse subnet key /coreos.com/network/subnets/10.0.0.0-33

Which isn't great behavior

I think that it shouldn't allocate a /33 (?1?!) lease and it should probably just exit