xonshのタブ補完でなんかエラーになる件

環境

• Windows 10 64bit
• Python 3.6.3
• xonsh: xonsh/0.6.0

事象

サブプロセスモードの何かしらで<TAB>で補完を試みると、下記のエラー

Exception in thread Thread-25:
Traceback (most recent call last):
  File "C:\Python36\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "C:\Python36\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Python36\lib\subprocess.py", line 1063, in _readerthread
    buffer.append(fh.read())
UnicodeDecodeError: 'cp932' codec can't decode byte 0x83 in position 14: illegal multibyte sequence

Exception in thread Thread-24:
Traceback (most recent call last):
  File "C:\Python36\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "C:\Python36\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Python36\lib\site-packages\prompt_toolkit\interface.py", line 865, in run
    completions = list(buffer.completer.get_completions(document, complete_event))
  File "C:\Python36\lib\site-packages\xonsh\ptk\completer.py", line 49, in get_completions
    self.ctx)
  File "C:\Python36\lib\site-packages\xontrib\free_cwd.py", line 82, in wrapper
    out = func(*args, **kwargs)
  File "C:\Python36\lib\site-packages\xonsh\completer.py", line 35, in complete
    out = func(prefix, line, begidx, endidx, ctx)
  File "C:\Python36\lib\site-packages\xonsh\completers\bash.py", line 13, in complete_from_bash
    command = xp.bash_command()
  File "C:\Python36\lib\site-packages\xonsh\platform.py", line 432, in bash_command
    bc = windows_bash_command()
  File "C:\Python36\lib\site-packages\xonsh\platform.py", line 340, in windows_bash_command
    universal_newlines=True)
  File "C:\Python36\lib\subprocess.py", line 336, in check_output
    **kwargs).stdout
  File "C:\Python36\lib\subprocess.py", line 405, in run
    stdout, stderr = process.communicate(input, timeout=timeout)
  File "C:\Python36\lib\subprocess.py", line 843, in communicate
    stdout, stderr = self._communicate(input, endtime, timeout)
  File "C:\Python36\lib\subprocess.py", line 1113, in _communicate
    stdout = stdout[0]
IndexError: list index out of range

原因

locale.getpreferredencoding()がcp932になっているので、Unicodeの文字をcp932でdecodeしようとしてる。(多分)

import locale

locale.getpreferredencoding()
\# => 'cp932'

対策

無理やりlocale.getpreferredencoding()を変更する

~/.xonshrcに以下を追記 (参考@stackoverflow)。

import _locale
_locale._getdefaultlocale = (lambda *args: ['ja_JP', 'utf_8'])