xlrd has removed support for anything other than xls files

[lordlouckster]

xlrd has explicitly removed support for anything other than xls files.
This causes error xlrd.biffh.XLRDError: Excel xlsx file; not supported on xlrd versions 2.0 and higher, since 2020 sheets are xlsx files.
Solutions:

1. Set requirements.txt to install xlrd version 1.2 (may expose potential security vulnerabilities, .xlsx files are zip files containing xml, both zip and xml have well published security issues that xlrd did a poor job of addressing)
2. Use openpyxl

[dlenski]

Option (1) done in 6b29810

A pull request for option (2) would be welcome 😁