W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-ru_RU) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-ru) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Ошибка GPG: http://ppa.launchpad.net/slytomcat/ppa/ubuntu trusty InRelease: Следующие подписи не могут быть проверены, так как недоступен открытый ключ: NO_PUBKEY D3F70009E9DD65EA
W: The repository 'http://ppa.launchpad.net/slytomcat/ppa/ubuntu trusty InRelease' is not signed.
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-ru_RU) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-ru) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/yandex-disk.list:1 and /etc/apt/sources.list.d/yandex.list:1
W: Ошибка GPG: http://ppa.launchpad.net/slytomcat/ppa/ubuntu trusty InRelease: Следующие подписи не могут быть проверены, так как недоступен открытый ключ: NO_PUBKEY D3F70009E9DD65EA
W: The repository 'http://ppa.launchpad.net/slytomcat/ppa/ubuntu trusty InRelease' is not signed.
а) насколько они критичны?
б) как избавится от них?