I guess the reason for that behavior is that in Xenial the package 'python-xdg' is not present by default.
Perhaps because in Xenial there is 'just' Python3 available per default?
The solution on my side is to install the package 'python-xdg'.
Then radiotray launches and works as expected.
So the global solution could be to change the program in order that 'python-xdg' is made available?!
I guess the reason for that behavior is that in Xenial the package 'python-xdg' is not present by default.
Perhaps because in Xenial there is 'just' Python3 available per default?
The solution on my side is to install the package 'python-xdg'.
Then radiotray launches and works as expected.
So the global solution could be to change the program in order that 'python-xdg' is made available?!
That's just my two cents.
Enjoy Ubuntu and enjoy radiotray :-).