If you use the included scripts, you should not have to interact with the virtual environment directly. This should help maintaining a separate, clean test environment.
If you want to install the Python dependencies globally on the system and not in a Python Virtual Environment you can examine the setupVenv.sh shell script to see how it executes pip to install them, and execute globally instead.
Using a Docker Container
Another option is to use a Docker Container. If you do, you will want to use persistent storage for asterisk and the testsuite. This can be done by mounting /usr/src/asterisk from the container onto either a bind mount or volume on the local OS.