Issue 49451 - Add environment markers to lib389 dependencies
Bug Description:
lib389 should be installable both on python2 and python3.
Currently it can be installed using python3 only because
of the python3-only dependencies.
Fix Description:
Use PEP-508 environment markers for setup.py and requirements.txt.
https://pagure.io/389-ds-base/issue/49451
Reviewed by: wibrown (Thanks!)