Information retrieved at the address: http://tomtomtom.org/networkmanager-openconnect/
It worked on the first try on my machine.
We remove unusable packages:
sudo apt-get purge network-manager-openconnect network-manager-openconnect-gnome
We compile the dependencies:
sudo apt-get build-dep network-manager-openconnect
The sources in apt must be active:
sudo sed -i s/#deb-src/deb-src/g /etc/apt/sources.list
We install the new dependencies:
sudo apt-get install libnm-dev
We retrieve the source code:
wget http://ftp.gnome.org/pub/GNOME/sources/NetworkManager-openconnect/1.1/NetworkManager-openconnect-1.1.93.tar.xz
We go to the directory:
cd NetworkManager-openconnect-1.1.93
We launch the configure:
./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --libexecdir=/usr/lib/NetworkManager/ --enable-more-warnings=yes --disable-static
We compile:
make
We install:
sudo make install
We install openconnect:
sudo apt-get install openconnect
We compile the package with checkinstall:
sudo checkinstall
We add a system user:
sudo adduser --system --quiet --home /var/lib/NetworkManager --no-create-home --gecos "NetworkManager OpenConnect plugin" --group nm-openconnect}
And we restart.