Toda vez que eu quero atualizar / instalar aplicativos sempre aparece um erro como este. Como faço para corrigir isso? guarnições

Question

Reading package lists... Done
Building dependency tree       
Reading state information... Done
N: Ignoring file 'docker.list.save.2' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.3' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.4' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.5' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.2' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.3' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.4' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension
N: Ignoring file 'docker.list.save.5' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension