openconnect zesty build

gistfile1.txt

$ sudo apt-get update
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://us.archive.ubuntu.com/ubuntu xenial InRelease                                            
Hit:3 http://dl.google.com/linux/chrome/deb stable Release                                            
Get:4 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]                           
Hit:6 http://archive.ubuntu.com/ubuntu zesty InRelease                                                
Get:7 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]         
Get:8 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease [102 kB]                 
Fetched 306 kB in 1s (290 kB/s)                                    
Reading package lists... Done

$ sudo apt-get build-dep openconnect
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 builddeps:openconnect : Depends: debhelper (>= 10) but 9.20160115ubuntu3 is to be installed
E: Unable to correct problems, you have held broken packages.

$ sudo apt-get -b source -t zesty openconnect
Reading package lists... Done
E: The value 'zesty' is invalid for APT::Default-Release as such a release is not available in the sources
E: Unable to find a source package for 
$