python bindings: use assertTrue instead ot assert_
python bindings: use assertTrue instead ot assert_

assert_ is deprecated in python3

oaubert/python-vlc,geoffsalmon/vlc-python,oaubert/python-vlc,kermit666/vlc-bindings-python,kermit666/vlc-bindings-python,geoffsalmon/vlc-python,pombreda/git.videolan.org-vlc-bindings-python,pombreda/git.videolan.org-vlc-bindings-python,metakermit/vlc-bindings-python,metakermit/vlc-bindings-python