One of the devtests (the python_api_test) gets skipped without failures
if the uhd module can't be loaded. However, this can mask errors if the
uhd module can't be loaded because it's broken. This change will verify
if the uhd module should have been loaded, and throw an error if that's
the case.
This changes two things in all applicable files:
- Remove imports from __future__
- Change default shebangs from /usr/bin/env python to /usr/bin/env
python3
Usually, devtest is run via make (or ninja), and will use the correct
Python interpreter. When running directly on the command line, it is
important to pick the right Python interpreter so it will work with the
Python API.
Here, we change the default interpreter from Python 2 to 3, because
that's the more common version, and will be the only option for upcoming
UHD 4.0 anyway.
