Python missing?

[j2l]

Hello!
I noticed a glitch with the docker image, I get:
docker logs hubot

> webworker-threads@0.7.17 install /home/hubotnat/bot/node_modules/webworker-threads
> node-gyp rebuild

gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "python", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/configure.js:483:19)
gyp ERR! stack     at PythonFinder.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/configure.js:397:16)
gyp ERR! stack     at F (/usr/local/lib/node_modules/npm/node_modules/which/which.js:68:16)
gyp ERR! stack     at E (/usr/local/lib/node_modules/npm/node_modules/which/which.js:80:29)
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/which/which.js:89:16
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/which/node_modules/isexe/index.js:42:5
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/which/node_modules/isexe/mode.js:8:5
gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:166:21)
gyp ERR! System Linux 3.16.0-7-amd64
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /home/hubotnat/bot/node_modules/webworker-threads
gyp ERR! node -v v9.4.0
gyp ERR! node-gyp -v v3.6.2
gyp ERR! not ok
npm WARN hubot-help@0.2.2 requires a peer of coffee-script@^1.12.6 but none is installed. You must install peer dependencies yourself.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: webworker-threads@0.7.17 (node_modules/webworker-threads):
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: webworker-threads@0.7.17 install: `node-gyp rebuild`
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: Exit status 1

added 9 packages, removed 9 packages and updated 1 package in 10.691s
[Thu Dec 20 2018 10:05:53 GMT+0000 (GMT)] DEBUG Loading adapter rocketchat
[Thu Dec 20 2018 10:05:54 GMT+0000 (GMT)] INFO Starting Rocketchat adapter version 1.0.12...
[Thu Dec 20 2018 10:05:54 GMT+0000 (GMT)] INFO Once connected to rooms I will respond to the name: HubotNatural
[Thu Dec 20 2018 10:05:54 GMT+0000 (GMT)] INFO I will also respond to my Rocket.Chat username as an alias: Lane
[Thu Dec 20 2018 10:05:54 GMT+0000 (GMT)] INFO Connecting To: rocketchat:3000
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Successfully connected!
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Logging In
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Successfully Logged In
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO rid:  []
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO All rooms joined.
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Preparing Meteor Subscriptions..
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Subscribing to Room: __my_messages__
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Successfully subscribed to messages
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] INFO Setting up reactive message list...
[Thu Dec 20 2018 10:07:17 GMT+0000 (GMT)] DEBUG Loading scripts from /home/hubotnat/bot/scripts
Loading corpus: /home/hubotnat/bot/training_data/corpus.yml
[Thu Dec 20 2018 10:07:18 GMT+0000 (GMT)] INFO Calling: getUserRoles,
Processing interactions

Any idea?
Thx