运行 $ juju quickstart 时出错。我怀疑 maas 安装存在问题，但找不到任何问题。
juju quickstart v2.2.4
ssh-agent has been started.
To interact with Juju or quickstart again after quickstart
finishes, please run the following in a terminal to start ssh-agent:
eval `ssh-agent`
bootstrapping the maas environment
juju-quickstart: error: Bootstrapping environment "maas"
Starting new instance for initial state server
Launching instance
WARNING no architecture was specified, acquiring an arbitrary node
- /MAAS/api/1.0/nodes/node-8a3bd444-4d91-11e6-aa49-ecb1d76ea468/
Installing Juju agent on bootstrap instance
Waiting for address
Attempting to connect to 10.1.1.151:22
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
37:0d:79:f3:09:03:b0:1c:98:ae:7e:eb:81:c2:17:83.
Please contact your system administrator.
Add correct host key in /home/student/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/student/.ssh/known_hosts:1
remove with: ssh-keygen -f "/home/student/.ssh/known_hosts" -R 10.1.1.151
Keyboard-interactive authentication is disabled to avoid man-in-the-middle attacks.
bash: warning: setlocale: LC_ALL: cannot change locale (en_IN)
/bin/bash: warning: setlocale: LC_ALL: cannot change locale (en_IN)
Logging to /var/log/cloud-init-output.log on remote host
Running apt-get update
Running apt-get upgrade
Installing package: curl
Installing package: cpu-checker
Installing package: bridge-utils
Installing package: rsyslog-gnutls
Installing package: cloud-utils
Installing package: cloud-image-utils
Installing package: tmux
Fetching tools: curl -sSfw 'tools from %{url_effective} downloaded: HTTP %{http_code}; time %{time_total}s; size %{size_download} bytes; speed %{speed_download} bytes/s ' --retry 10 -o $bin/tools.tar.gz <[https://streams.canonical.com/juju/tools/agent/1.25.5/juju-1.25.5-trusty-amd64.tgz]>
Write failed: Broken pipe
ERROR failed to bootstrap environment: subprocess encountered error code 255
我该如何解决这个问题？