Did it ^^

2.1.2-xenial-amd64

enable-os-upgrade:false image-stream:daily apt-https-proxy: apt-mirror: net-bond-reconfigure-delay:17 logging-config: resource-tags: development:false logforward-enabled:false ssl-hostname-verification:true automatically-retry-hooks:true name:controller image-metadata-url: type:maas http-proxy: ignore-machine-addresses:false enable-os-refresh-update:true disable-network-management:false no-proxy: default-series:xenial ftp-proxy: transmit-vendor-metrics:true provisioner-harvest-mode:destroyed]
22:28:05 DEBUG juju.provider.maas environprovider.go:51 opening model "controller".
22:28:05 INFO  cmd cmd.go:129 Creating Juju controller "juju-ctrl" on maas
22:28:05 INFO  juju.cmd.juju.commands bootstrap.go:526 combined bootstrap constraints: 
22:28:05 DEBUG juju.environs.bootstrap bootstrap.go:199 model "controller" supports service/machine networks: true
22:28:05 DEBUG juju.environs.bootstrap bootstrap.go:201 network management by juju enabled: true
22:28:05 INFO  cmd cmd.go:141 Loading image metadata
22:28:05 INFO  cmd cmd.go:129 Looking for packaged Juju agent version 2.1.2 for amd64
22:28:05 INFO  juju.environs.bootstrap tools.go:72 looking for bootstrap agent binaries: version=2.1.2
22:28:05 INFO  juju.environs.tools tools.go:101 finding agent binaries in stream "released"
22:28:05 INFO  juju.environs.tools tools.go:103 reading agent binaries with major.minor version 2.1
22:28:05 INFO  juju.environs.tools tools.go:111 filtering agent binaries by version: 2.1.2
22:28:05 INFO  juju.environs.tools tools.go:114 filtering agent binaries by series: xenial
22:28:05 INFO  juju.environs.tools tools.go:117 filtering agent binaries by architecture: amd64
22:28:05 DEBUG juju.environs.tools urls.go:109 trying datasource "keystone catalog"
22:28:05 DEBUG juju.environs.simplestreams simplestreams.go:680 using default candidate for content id "com.ubuntu.juju:released:tools" are {20161007 mirrors:1.0 content-download streams/v1/cpc-mirrors.sjson []}
22:28:06 INFO  juju.environs.bootstrap tools.go:74 found 1 packaged agent binaries
22:28:06 INFO  cmd cmd.go:141 Starting new instance for initial controller
Launching controller instance(s) on maas...
22:28:06 DEBUG juju.cloudconfig.instancecfg instancecfg.go:781 Setting numa ctl preference to false
22:28:06 DEBUG juju.service discovery.go:63 discovered init system "systemd" from series "xenial"
22:28:06 DEBUG juju.provider.maas environ.go:1001 maas user data; 2024 bytes
22:28:07 DEBUG juju.provider.maas environ.go:1033 started instance "p4cawt"
 - p4cawt (arch=amd64 mem=3.8G cores=1)
22:28:07 INFO  juju.environs.bootstrap bootstrap.go:601 newest version: 2.1.2
22:28:07 INFO  juju.environs.bootstrap bootstrap.go:616 picked bootstrap tools version: 2.1.2
22:28:07 INFO  juju.environs.bootstrap bootstrap.go:393 Installing Juju agent on bootstrap instance
22:28:08 INFO  cmd cmd.go:129 Fetching Juju GUI 2.5.0
...

No change. it is still stuck at the same step, Where does it fetch JUJU GUI ? I am thinking about a network problem but I do not understand why.

If I cancel the provisionning, I get the following : 

22:44:39 INFO  juju.provider.common destroy.go:20 destroying model "controller"
22:44:39 INFO  juju.provider.common destroy.go:31 destroying instances
22:44:39 INFO  juju.provider.common destroy.go:51 destroying storage
22:44:39 ERROR cmd supercommand.go:458 failed to bootstrap model: bootstrap instance started but did not change to Deployed state: instance "p4cawt" is started but not deployed
22:44:39 DEBUG cmd supercommand.go:459 (error details: [{github.com/juju/juju/cmd/juju/commands/bootstrap.go:574: failed to bootstrap model} {github.com/juju/juju/provider/maas/environ.go:173: bootstrap instance started but did not change to Deployed state} {github.com/juju/juju/provider/maas/environ.go:1176: instance "p4cawt" is started but not deployed}])

(and github.com/juju/juju/provider/maas/environ.go is reachable :
wget http://github.com/juju/juju/provider/maas/environ.go
--2017-04-12 22:58:34--  http://github.com/juju/juju/provider/maas/environ.go
Resolving github.com (github.com)... 192.30.253.113, 192.30.253.112
Connecting to github.com (github.com)|192.30.253.113|:80... connected)

I am lost ^^