Fails packaging on Python 3.8 - no 'importlib.resources.files'

[tmontes]

REPORTED by @tjguk, on Gitter's mu-editor/dev channel:

I gave it a go on Windows. Cloned pup; created a local venv; pip install -e.[dev]; and then ran -- from the pup directory pup package --launch-module=mu c:\work-in-progress\mu-master
It did stuff for a while (albeit with no output) and then I got an error:
20200915 072004 E pup Execution failure: module 'importlib.resources' has no attribute 'files'
This is with Python 3.8.3 on Win10

TO WHICH I RESPONDED:

Thanks for trying it @tjguk! :) Silly me trying to use 3.8 stdlib’s importlib.resources, while using PyPI’s “backported” but more capable on 3.7 - will be an easy fix. FYI, for more “noisy” output, add —log-level=info/debug between pup and package.

FACTS:

• importlib.resources is used to "bundle" cookiecutter templates as packages within pup itself.
• On 3.7 the PyPI backported importlib_resources package is used...
• ...on 3.8, the standard library's importlib.resources is used instead.

CULPRIT:

• The PyPI importlib_resources provides a files function that is not implemeted by 3.8's stdlib.

POSSIBLE FIXES:

• Use PyPI's importlib_resources on both 3.7 and 3.8 (3.9's stdlib seems to include the files function we're using).
• Use alternative implementation, supported by 3.8's stdlib.

[tmontes]

THOUGHT + DECISION:

• Given that 3.9 stdlb includes importlib.resources.files, we'll go ahead and use that into the future.
• The fix is, thus, using PyPI's importlib_resources with 3.8.