replace 'jessie' with 'stretch' in Debian install instructions

content/install.rst

@@ -64,15 +64,15 @@ packages we provide.  We target Debian "stable" and Debian "testing", but our
 packages may also work on many other recent Debian-derived distributions as
 well.
 
-The following instructions will install Kwant on Debian stable "jessie".
+The following instructions will install Kwant on Debian stable "stretch".
 They need to be executed as root.
-(To install on Debian testing "stretch", repace "jessie-backports" with "testing".)
+(To install on Debian testing "buster", repace "stretch-backports" with "testing".)
 
 1. Add the following lines to ``/etc/apt/sources.list``::
 
-       deb http://ftp.debian.org/debian jessie-backports main
-       deb http://downloads.kwant-project.org/debian/ jessie-backports main
-       deb-src http://downloads.kwant-project.org/debian/ jessie-backports main
+       deb http://ftp.debian.org/debian stretch-backports main
+       deb http://downloads.kwant-project.org/debian/ stretch-backports main
+       deb-src http://downloads.kwant-project.org/debian/ stretch-backports main
 
 2. (Optional) Add the OpenPGP key used to sign the repositories by executing::
 
@@ -84,7 +84,7 @@ They need to be executed as root.
 3. Update the package data, and install Kwant::
 
        apt-get update
-       apt-get -t jessie-backports install python3-kwant python-kwant-doc
+       apt-get -t stretch-backports install python3-kwant python-kwant-doc
 
    The ``python-kwant-doc`` package is optional and installs the HTML
    documentation of Kwant in the directory ``/usr/share/doc/python-kwant-doc``.