zoneinfo issues for Python versions 3.9 and below

[BrQE]

fixed zoneinfo issues for Python versions 3.9 and below.

[farahats9]

Thank you for your contribution, zoneinfo is already supported in Python 3.9+
This appears to add an external package backports.zoneinfo and it needs to be conditional based on python version for 3.8 and below only, can you update you PR to add these changes?

[BrQE]

Of cource, updated PR, I thank you, especially, for deciding to update this library.

[farahats9]

Sorry I wasn't clear, your original code was correct. I meant it should be added in the setup.py and the requirements files as a conditional based on the version of python it should install these backports dependencies.