sudo not respecting /etc/sudoers

[Avinash Sonawane <rootkea@gmail.com>]

Hello! I am using Debian Jessie with Xfce.

I am using proxy to access the Internet. Here's my /etc/environment
http://paste.debian.net/170960

Whenever I say `$ sudo apt-get update` it says
"Err http://security.debian.org jessie/updates Release.gpg
  Could not resolve 'security.debian.org'
Err http://ftp.us.debian.org jessie Release.gpg
  Could not resolve 'ftp.us.debian.org'
..."

But whenever I say "# apt-get update" the proxy works and packages get
fetched properly.

After searching on the web I came to know that `sudo` does not carry
the environment
https://wiki.archlinux.org/index.php/Sudo#Environment_variables and
also found out that to make `sudo` acrry the environment one should
add `
Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"` to
/etc/sudoers (the recommended way according to arch wiki).

So I changed my /etc/sudoers. Here is it http://paste.debian.net/170961/

But still `$ sudo apt-get update` produces above error. And it's
really an inconvenience for me to become root user to do apt thing.

So why `sudo` not respecting `/etc/sudoers` ? Am I missing something?

Thank you.
-- 
Avinash Sonawane (RootKea)
PICT, Pune
http://rootkea.wordpress.com