Added support for writing formula-value tuples
Created originally on Bitbucket by cliffckerr (Cliff Kerr)
Changesets for this Pull Request have not been imported, because it had been already declined on Bitbucket. Marked as closed by the import user.
This small PR adds support for writing both formulas and calculated values. All that is required is to supply a tuple for the cell value, which is parsed as a formula and calculated value, instead of raising an error as it did before. This addresses:
and
https://bitbucket.org/openpyxl/openpyxl/issues/251/add-a-value-cache-to-cellcell