So, I was using pipenv 3.1.* or 3.2.*, now I'm using pipenv==3.3.3 on macOS Sierra.

And this happens:

Creating a Pipfile for this project...
Creating a virtualenv for this project...
Traceback (most recent call last):
  File "/usr/local/bin/pew", line 7, in <module>
    from pew.pew import pew
  File "/usr/local/lib/python2.7/site-packages/pew/", line 11, in <module>
    from . import pew
  File "/usr/local/lib/python2.7/site-packages/pew/", line 36, in <module>
    from pew._utils import (check_call, invoke, expandpath, own, env_bin_dir,
  File "/usr/local/lib/python2.7/site-packages/pew/", line 22, in <module>
    encoding = locale.getlocale()[1] or 'ascii'
  File "/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/", line 564, in getlocale
    return _parse_localename(localename)
  File "/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/lib/python2.7/", line 477, in _parse_localename
    raise ValueError, 'unknown locale: %s' % localename
ValueError: unknown locale: UTF-8

A strange thing, since I didn't changed anything on macOS locale settings, but I've fixed by adding, on my ~/.bash_profile (~/.zshrc):

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

I don't know if anyone will have the same issue, but if this is not something for pipenv to bypass without error or something, you can close the issue. =]