我正在使用debian V 8，在更新系统时出现一些错误，我该如何解决？
我已经尝试更改我的来源列表，但没有成功
Err http://ppa.launchpad.net jessie/main amd64 Packages
404 Not Found
Ign http://ppa.launchpad.net jessie/main Translation-en_US
Ign http://ppa.launchpad.net jessie/main Translation-en
Err http://ppa.launchpad.net jessie/main amd64 Packages
404 Not Found
Ign http://ppa.launchpad.net jessie/main Translation-en_US
Ign http://ppa.launchpad.net jessie/main Translation-en
Fetched 65.8 kB in 28s (2,307 B/s)
W: Failed to fetch
http://ppa.launchpad.net/ondrej/php/ubuntu/dists/jessie/main/binary-
amd64/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/ondrej/php-
qa/ubuntu/dists/jessie/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old
ones used instead.
这是我的来源
# deb cdrom:[Debian GNU/Linux 8.2.0 _Jessie_ - Official amd64 DVD Binary-
1 20150906-11:13]/ jessie contrib main
deb http://ftp.debian.org/debian/ jessie main contrib non-free
deb-src http://ftp.debian.org/debian/ jessie main contrib non-free
deb http://security.debian.org/ jessie/updates main contrib
deb-src http://security.debian.org/ jessie/updates main contrib
# jessie-updates, previously known as 'volatile'
# A network mirror was not selected during install. The following entries
# are provided as examples, but you should amend them as appropriate
# for your mirror of choice.