juju-quickstart fails to start in UTF-8 systems

The command "juju-quickstart" fails to start when LC_ALL is set to use unicode output locales but works fine if a not-UTF8 locale is setted. The

Juju-Quickstart is in version 2.2.1+bzr140+ppa38~ubuntu15.04.1 and Python is version 2.7.9.

The bug can be easily replicated:

~$ export LC_ALL=pt_BR.UTF-8
~$ juju-quickstart
Traceback (most recent call last):
  File "/usr/bin/juju-quickstart", line 32, in <module>
    options = manage.setup()
  File "/usr/lib/python2.7/dist-packages/quickstart/manage.py", line 394, in setup
    default_env_name = envs.get_default_env_name()
  File "/usr/lib/python2.7/dist-packages/quickstart/models/envs.py", line 117, in get_default_env_name
    retcode, output, _ = utils.call('juju', 'switch')
  File "/usr/lib/python2.7/dist-packages/quickstart/utils.py", line 92, in call
    return 127, '', '{}: {}'.format(command, err)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 26: ordinal not in range(128)
~$ env | grep LANG
LANG=pt_BR.UTF-8
...
~$ export LANG=pt_BR
~$ juju-quickstart
interactive session closed
quitting'''