Further work on details + adaptation to Python 3.9.

I got annoying problems with xlrd, so this will be the last commit with a code using xlrd. It seems to work, but only to due to a workaround in embermaker.helpers as explained here
https://stackoverflow.com/questions/64264563/attributeerror-elementtree-object-has-no-attribute-getiterator-when-trying/65131301#65131301
2 jobs for 1.4.0b1 in 55 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Build
passed wheel #1201777

00:00:35

 
  Deploy
failed deploy_PyPI #1201778

00:00:19

 
Name Stage Failure
failed
deploy_PyPI Deploy
$ twine upload dist/*
Uploading distributions to https://upload.pypi.org/legacy/
Uploading EmberFactory-1.4.0b1-py3-none-any.whl
0%| | 0.00/389k [00:00<?, ?B/s] 2%|▏ | 8.00k/389k [00:00<00:17, 22.3kB/s] 23%|██▎ | 88.0k/389k [00:00<00:09, 31.5kB/s] 37%|███▋ | 144k/389k [00:00<00:05, 43.9kB/s] 70%|██████▉ | 272k/389k [00:00<00:01, 61.8kB/s] 100%|██████████| 389k/389k [00:00<00:00, 428kB/s]
NOTE: Try --verbose to see response content.
HTTPError: 403 Forbidden from https://upload.pypi.org/legacy/
Invalid or non-existent authentication information. See https://pypi.org/help/#invalid-auth for more information.
Cleaning up file based variables
ERROR: Job failed: exit code 1