Hit:1 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu focal InRelease
Hit:2 http://de.archive.ubuntu.com/ubuntu focal InRelease
Hit:3 https://cloud.r-project.org/bin/linux/ubuntu focal-cran40/ InRelease
Get:4 http://de.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Get:5 http://de.archive.ubuntu.com/ubuntu focal-backports InRelease [108 kB]
Get:6 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Fetched 336 kB in 1s (373 kB/s)
Reading package lists...
Error: `.` must contain a package.
Execution halted