Let the built-in ubuntu-drivers program decide automatically which graphics driver to install. Open the terminal and type:
sudo ubuntu-drivers autoinstall
The autoinstall command of ubuntu-drivers installs drivers that are appropriate for automatic installation including their dependencies.
The PPA you have added does not contain packages for your release, so you need to remove it first:
sudo add-apt-repository -r ppa:v-launchpad-jochen-sprickerhof-de/pcl
sudo apt-get update
I have never used PCL, but it is packaged in official repositories (see its source pcl package).
The simplest method would be to install the metapackage
After looking at the first link in your error message, getting into the dists directory, it seems that this PPA does not support Xenial, as there is indeed no such directory.
This link however, provides a link to a pre-built DEB file you can download and install using dpkg (not recommended as it is just a Dropbox link and the file could contain malicious ...
I ran into the same issue. Turned out the cause was that /usr/bin/python3 was not linked to an executable.
Here's how to solve it:
Install Python if you have not done so.
Pick the Python executable you want to use, say python3.5. Go to /usr/bin and you'll see installed executable like python2.7, python3.5, python3.6.
Run the following command, assuming ...