Invoke: DeprecationWarning on usage of imp in loader.py

[milliams]

When running my test suite which uses invoke (via fabric) I see:

======================= warnings summary ========================
venv/lib64/python3.7/site-packages/invoke/loader.py:3
  venv/lib64/python3.7/site-packages/invoke/loader.py:3: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
    import imp

-- Docs: https://docs.pytest.org/en/latest/warnings.html
========== 6 passed, 1 warnings in 1651.00s (0:27:30) ===========

The used parts of the imp module have been deprecated since Python 3.3 and the replacement importlib has been available since Python 3.1.

[SwampFalc]

For what it's worth, there's a workaround that will suppress that one particular warning. I use it on pytest but I believe it's going to be mostly the same with other test frameworks:

-W ignore::DeprecationWarning:invoke.loader

[rupertnash]

I have also spotted this - the question is really: which versions of python is invoke committed to supporting? The docs say 2.7 and >=3.4. However, we have now passed 2020-01-01, so the sun has officially gone down on python 2. If I had a vote (which I don't obviously), it would be to drop support for 2.7 and switch this code to importlib

Instead I'm adding a warning filter (https://docs.pytest.org/en/latest/warnings.html#pytest-mark-filterwarnings) and have logged an issue on our project.