The package system is broken (with package ethereum-swarm)

I removed the ethereum ppa with sudo add-apt-repository --remove ppa:ethereum/ethereum and then had to run sudo apt-get -f install as the error message suggested, before any other apt commands would complete. Then I could run sudo apt-get purge swarm successfully, and then I could run sudo apt upgrade. I couldn't comment on what things are necessary or sufficient, though.

Three options here:

• ask package authors about conflict between their ethereum-swarm and ubuntu package swarm.

• remove standart swarm Ubuntu package and then install ethereum-swarm:

  sudo apt-get purge swarm
  sudo apt-get install ethereum-swarm
  

• force installation of ethereum-swarm (you take this risk, as this is not recommended):

  sudo dpkg -i --force-all \
  /var/cache/apt/archives/ethereum-swarm_0.3.1+build14601+xenial_amd64.deb
  

  then remove swarm package with sudo apt-get purge swarm and reinstall sudo apt-get install --reinstall ethereum-swarm again (to keep system clean).