For further testing in case the issue was with the snap I used; it appears to fail for any snap:


ubuntu@vital-calf:~$ sudo snap login
[...]
Login successful
ubuntu@vital-calf:~$ wget http://people.canonical.com/~mtrudel/subiquity_0.20_amd64.snap
--2017-03-09 02:40:07--  http://people.canonical.com/~mtrudel/subiquity_0.20_amd64.snap
Resolving people.canonical.com (people.canonical.com)... 91.189.89.62
Connecting to people.canonical.com (people.canonical.com)|91.189.89.62|:80... ^C
ubuntu@vital-calf:~$ http_proxy="http://192.168.254.254:8000/" wget http://people.canonical.com/~mtrudel/subiquity_0.20_amd64.snap
--2017-03-09 02:40:28--  http://people.canonical.com/~mtrudel/subiquity_0.20_amd64.snap
Connecting to 192.168.254.254:8000... connected.
Proxy request sent, awaiting response... 200 OK
Length: 20377600 (19M)
Saving to: ‘subiquity_0.20_amd64.snap’

subiquity_0.20_amd64.snap                       100%[=====================================================================================================>]  19.43M   730KB/s    in 33s     

2017-03-09 02:41:01 (605 KB/s) - ‘subiquity_0.20_amd64.snap’ saved [20377600/20377600]

ubuntu@vital-calf:~$ sudo snap find 
sudo: unable to resolve host vital-calf
Name               Version   Developer   Notes  Summary
docker             1.11.2-9  docker-inc  -      The docker app deployment mechanism
lxd                2.8       canonical   -      System container manager and API
mongo32            3.2.7     niemeyer    -      MongoDB document-oriented database
rocketchat-server  0.53.0    rocketchat  -      Group chat server for 100s,  installed in seconds.
ubuntu@vital-calf:~$ sudo snap find hello-world
sudo: unable to resolve host vital-calf
Name                                 Version    Developer           Notes    Summary
[...]
hello-world                          6.3        canonical           -        The 'hello-world' of snaps
[...]
hello-classic-tomechangosubanana-1   2          tomechangosubanana  classic  say hello classic
[...]
ubuntu@vital-calf:~$ sudo snap install hello-world
sudo: unable to resolve host vital-calf
hello-world 6.3 from 'canonical' installed
ubuntu@vital-calf:~$ /snap/bin/hello-world
cannot create namespace group directory /run/snapd/ns: Bad file descriptor
ubuntu@vital-calf:~$ sudo /snap/bin/hello-world
sudo: unable to resolve host vital-calf
cannot create namespace group directory /run/snapd/ns: Bad file descriptor
ubuntu@vital-calf:~$ sudo snap install hello-classic-tomechangosubanana-1
sudo: unable to resolve host vital-calf
error: snap "hello-classic-tomechangosubanana-1" requires classic or confinement override
ubuntu@vital-calf:~$ sudo snap install --classic hello-classic-tomechangosubanana-1
sudo: unable to resolve host vital-calf
hello-classic-tomechangosubanana-1 2 from 'tomechangosubanana' installed                     
ubuntu@vital-calf:~$ /snap/bin/hello-classic-tomechangosubanana-1.hello 
cannot create user data directory: /home/ubuntu/snap/hello-classic-tomechangosubanana-1/2: Bad file descriptor
ubuntu@vital-calf:~$ sudo snap install --classic --dangerous subiquity_0.20_amd64.snap
sudo: unable to resolve host vital-calf
subiquity 0.20 installed
ubuntu@vital-calf:~$ /snap/bin/subiquity
cannot create user data directory: /home/ubuntu/snap/subiquity/x1: Bad file descriptor
ubuntu@vital-calf:~$ /snap/bin/subiquity --dry-run
cannot create user data directory: /home/ubuntu/snap/subiquity/x1: Bad file descriptor