ascii can't decode error in 14.04 server install

[Impact]

Running juju-quickstart from a machine without locales installed and properly configured causes a traceback.

[Test Case]

Using juju-quickstart with the patch applied the following should not exit:

LC_ALL=C juju-quickstart -i

[Regression Potential]

The patch attempts to set encoding using urwid. If it fails the user is warned rather than the application printing a traceback. Regression potential is minimal.

[Original Bug Report]

Reported from a user in irc. They attempted to use juju-quickstart on 14.04 server install and got the following trace.

$ 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 427, in setup
_setup_env(options, parser)
File "/usr/lib/python2.7/dist-packages/quickstart/manage.py", line 276, in _setup_env
parser, env_type_db, env_db, env_file)
File "/usr/lib/python2.7/dist-packages/quickstart/manage.py", line 206, in _start_interactive_session
views.env_index, env_type_db, env_db, save_callable)
File "/usr/lib/python2.7/dist-packages/quickstart/cli/views.py", line 128, in show
loop.run()
File "/usr/lib/python2.7/dist-packages/urwid/main_loop.py", line 272, in run
self.screen.run_wrapper(self._run)
File "/usr/lib/python2.7/dist-packages/urwid/raw_display.py", line 242, in run_wrapper
return fn()
File "/usr/lib/python2.7/dist-packages/urwid/main_loop.py", line 312, in _run
self.draw_screen()
File "/usr/lib/python2.7/dist-packages/urwid/main_loop.py", line 563, in draw_screen
canvas = self._topmost_widget.render(self.screen_size, focus=True)
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 141, in cached_render
canv = fn(self, size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/container.py", line 755, in render
self.top_w_size(size, left, right, top, bottom), focus)
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 141, in cached_render
canv = fn(self, size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/container.py", line 1049, in render
focus and self.focus_part == 'header')
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 141, in cached_render
canv = fn(self, size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/container.py", line 1493, in render
canv = w.render((maxcol,), focus=focus and item_focus)
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 141, in cached_render
canv = fn(self, size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/decoration.py", line 225, in render
canv = self._original_widget.render(size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 141, in cached_render
canv = fn(self, size, focus=focus)
File "/usr/lib/python2.7/dist-packages/urwid/widget.py", line 751, in render
canv = SolidCanvas(self.div_char, maxcol, 1)
File "/usr/lib/python2.7/dist-packages/urwid/canvas.py", line 495, in __init__
self._text, cs = apply_target_encoding(fill_char[:end])
File "/usr/lib/python2.7/dist-packages/urwid/util.py", line 121, in apply_target_encoding
s = s.encode( _target_encoding )
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2582' in position 0: ordinal not in range(128)