This is due to the fact that you have installed some packages from the
Ubuntu toolchain PPA and they provide a greater version of the package
than the one in Ubuntu 18.04, the release to which you are trying to
upgrade. Please use the tool ppa-purge to remove that PPA and downgrade
to the official
** Tags added: artful2bionic
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https://bugs.launchpad.net/bugs/1770847
Title:
ubuntu 18.04
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That is what heppen so often when ppa is used:
ERROR IOError/SystemError in cache.update(): 'E:The repository
'http://ppa.launchpad.net/jonathonf/gcc-7.1/ubuntu artful Release' does
not have a Release file.
So use ppa-purge to downgrade the ppa's packages to genuine version;
then clean the system
