"config failed" when configuring webcam-webui example

I tried to build the webcam-webui example code at:

https://github.com/ubuntu-core/snapcraft/tree/master/examples/webcam-webui

In the end, I installed it to the KVM environment:

(amd64)ubuntu@localhost:~$ snappy list -v
Name Date Version Developer
ubuntu-core 2015-11-13 10 ubuntu*
ubuntu-core 2015-10-23 9 ubuntu
config-example 2015-11-25 1.0.6 canonical*
hello-world 2015-11-03 IEYVCgYIIDJe sideload*
hello-world 2015-11-03 IEYVDLXLHXJD sideload
hello-xiaoguo 2015-11-05 IEeNDQQRGSGL sideload
hello-xiaoguo 2015-11-05 IEeNEfBRVYGe sideload*
mqtt-piglow 2015-11-23 IGJVDbJOQafg sideload
mqtt-piglow 2015-11-23 IGJVJYLbWCaC sideload*
pastebinit 2015-11-02 1.4.0.0.2 mvo*
webcam-webui 2015-11-25 IGPIKAOFafGQ sideload*
webcam 2015-11-14 IFUaQLgTUKSU sideload*
webdm 2015-10-23 0.9.2 canonical*
generic-amd64 2015-10-23 1.4 canonical*
(amd64)ubuntu@localhost:~$ sudo snappy service status webcam-webui
Snap Service State
webcam-webui webcam-webui enabled; loaded; active (running)

I am trying to dump a configuration from the example:

(amd64)ubuntu@localhost:~$ snappy config webcam-webui > my.yaml
config failed with: '/apps/webcam-webui.sideload/IGPIKAOFafGQ/meta/hooks/config: 8: exec: usr/bin/config.py: not found
' (exit status 127)

Then, I get the above error.