Misleading error when trying to read password-protected workbooks

[wurli]

When trying to read a password-protected workbook I get the following error:

Error:
! The file format does not appear to be xlsx, xlsm, xltx or xltm,
even if the filename extension says so.
  some-workbook.xlsm
You could try converting it with a spreadsheet application.
If you need tidyxl to support files of this type, then please open an issue at https://github.com/nacnudus/tidyxl/issues.

In this case the error is a bit misleading, as in reality the workbook is in the correct format, but the protection needs to be removed.