Previously discussed in #199

See theskumar/python-dotenv#297

It looks like now there is https://github.com/theskumar/python-dotenv/pull/388/files which will cause load_dotenv to return false if no vars were read:

import dotenv
a=dotenv.load_dotenv('no.env', verbose=True)
print(a)
False

So for the reasons previously described it would be good to have a way in environs to force a failure if the specified env file does not exist, by e.g. checking the return code from dotenv and raising an exception if it is false.