Ubuntu下使用 source /etc/sudoers 命令报一下错误怎么解决?

Ubuntu下使用 source /etc/sudoers 命令报一下错误怎么解决?
WARNING:root:could not open file '/etc/apt/sources.list'

No command 'Defaults' found, did you mean:
Command 'defaults' from package 'gnustep-base-runtime' (universe)
Defaults: command not found
WARNING:root:could not open file '/etc/apt/sources.list'

No command 'Defaults' found, did you mean:
Command 'defaults' from package 'gnustep-base-runtime' (universe)
Defaults: command not found
WARNING:root:could not open file '/etc/apt/sources.list'

No command 'Defaults' found, did you mean:
Command 'defaults' from package 'gnustep-base-runtime' (universe)
Defaults: command not found
-su: /etc/sudoers: line 20: syntax error near unexpected token ('
-su: /etc/sudoers: line 20:root ALL=(ALL:ALL) ALL'

http://blog.csdn.net/github_22672485/article/details/40584173

请问解决了吗，碰到了同样的问题