Warn pipenv and black users when LC_ALL isn't set

[brettcannon]

See #1027

[MikhailArkhipov]

Probably part of #648

[DonJayamanne]

The underlying problem is #1254
We're not logging any errors, its just being swallowed up.

[brettcannon]

If we do #1338 and log the entire environment then this can help with this as well by providing people with those details (but it's also a lot of info, so we might want to still limit what we send to the Output window).

[brettcannon]

Talking with Christian at the PyCon US sprints, Python 3.7 is setting LC_ALL=C.UTF-8 by default if it isn't overridden. So we might as well do this as well in other versions of Python when the user has not set it to avoid this issue with Click (we should also double-check that LANG does not need to be set, otherwise it can also be C.UTF-8).

[brettcannon]

What we might need to do is also provide whatever shell details we can to help people realize why when they have set their LC_ALL appropriately why it isn't being picked up. Best solution is to simply experiment and figure out whether the shell being used is login and/or interactive and tell people that they need to make sure to use the appropriate config file (e.g. .bashrc is not used in the same instances as .bash_profile for bash users).