pipenvでエラー"ValueError: unknown locale: UTF-8..."が出たときの対処法

対処したいエラー

Macでpipenvを使ってこんなエラーが出たときの対処法です。

$ pipenv shell
Traceback (most recent call last):
  File "/usr/local/bin/pipenv", line 11, in <module>
    sys.exit(cli())
  File "/usr/local/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.6/site-packages/pipenv/vendor/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/pipenv/cli.py", line 607, in shell
    three=three, python=python, fancy=fancy, shell_args=shell_args
  File "/usr/local/lib/python3.6/site-packages/pipenv/core.py", line 2148, in do_shell
    from .patched.pew import pew
  File "/usr/local/lib/python3.6/site-packages/pipenv/patched/pew/__init__.py", line 3, in <module>
    from . import pew
  File "/usr/local/lib/python3.6/site-packages/pipenv/patched/pew/pew.py", line 44, in <module>
    from pew._utils import (check_call, invoke, expandpath, own, env_bin_dir,
  File "/usr/local/lib/python3.6/site-packages/pipenv/patched/pew/__init__.py", line 3, in <module>
    from . import pew
  File "/usr/local/lib/python3.6/site-packages/pipenv/patched/pew/pew.py", line 44, in <module>
    from pew._utils import (check_call, invoke, expandpath, own, env_bin_dir,
  File "/usr/local/lib/python3.6/site-packages/pipenv/patched/pew/_utils.py", line 25, in <module>
    encoding = locale.getlocale()[1] or 'ascii'
  File "/usr/local/Cellar/python/3.6.5/Frameworks/Python.framework/Versions/3.6/lib/python3.6/locale.py", line 581, in getlocale
    return _parse_localename(localename)
  File "/usr/local/Cellar/python/3.6.5/Frameworks/Python.framework/Versions/3.6/lib/python3.6/locale.py", line 490, in _parse_localename
    raise ValueError('unknown locale: %s' % localename)
ValueError: unknown locale: UTF-8

対処法

以下を~/.bashrcに書けば追記すれば、エラーは起きなくなりました。

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

(参考 https://github.com/pypa/pipenv/issues/187#issuecomment-375172264)