special deployement needed for this:
------------------------------------
 $ sudo systemctl stop reproducible_build@startup.service >> document this in README or INSTALL

 * remove all jobs which match reproducible*testing*
 // hit all new jobs (to create chroots, etc) in:
 * https://jenkins.debian.net/view/reproducible/view/Debian_setup_amd64/
 * https://jenkins.debian.net/view/reproducible/view/Debian_setup_arm64/
 * https://jenkins.debian.net/view/reproducible/view/Debian_setup_armhf/
 * https://jenkins.debian.net/view/reproducible/view/Debian_setup_i386/
 $ sudo systemctl start reproducible_build@startup.service

changes not yet prepared in git
-------------------------------
completly prepare to add buster on 2017-06-17
(including changing the apache redirect testing→stretch to testing→buster)
finally, remove this file again.