Fix SyntaxWarning with python 3.8 due to using "is" in a literal comparison
Created originally on Bitbucket by aerostitch
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 PR fixes a SyntaxWarning you get when running openpyxl with python 3.8 due to using "is" in a literal comparison
The warning was:
SyntaxWarning: "is" with a literal. Did you mean "=="?