The dx-toolkit has been developed for some time with Python 3 support in mind (this includes, for example, importing from future amongst other recommendations).
As of November 2018, the dx-toolkit has been modified to support builds from Python 3 directly. These changes should address most issues with using dxpy and the dx-toolkit in Python 3 environments. To get started with installing the toolkit in Python 3 environments, use the pip command:
$ pip install dxpy
The CLI binaries are typically installed in $HOME/.local/bin. This may vary with your python installation; do: python -m site --user-base to find the location on your system.