Most likely, you will not be able to completely abandon Python 2, one way or another you will have to deal with it. However, this does not mean at all that it is worth refusing Python 3, there are not so many fundamental differences between these versions, and the main compatibility problem lies precisely in the modules.
For this, I would recommend learning both versions. Start, for example, with Python 3, and then learn the differences of versions . When the mass transition to Python 3 begins, I am sure you will need knowledge of both versions.
The most popular web frameworks for Python 3:
Bottle - Bottle is a fast, simple and lightweight WSGI micro web framework for Python. It is distributed as a single file module and has no dependencies.
Pyramid - Pyramid is a very general open source Python web framework. As a framework, it is easier to create an arbitrary web application. Wasn’t really important; it could be a spreadsheet, a corporate intranet, or a social networking platform. It can be used in a wide variety of circumstances.
CherryPy - CherryPy is a pythonic, object-oriented web framework. CherryPy Python program. This results in smaller source code developed in less time.