build: no need to support very old python versions
build: no need to support very old python versions

the subprocess module has been standard since python2.4, which has
been available in Ubuntu since at least 6.06.

cdsteinkuehler/MachineKit,bobvanderlinden/machinekit,narogon/linuxcnc,cdsteinkuehler/MachineKit,araisrobo/machinekit,strahlex/machinekit,ikcalB/linuxcnc-mirror,unseenlaser/machinekit,ArcEye/machinekit-testing,cnc-club/linuxcnc,strahlex/machinekit,unseenlaser/machinekit,ikcalB/linuxcnc-mirror,aschiffler/linuxcnc,cdsteinkuehler/MachineKit,narogon/linuxcnc,jaguarcat79/ILC-with-LinuxCNC,RunningLight/machinekit,narogon/linuxcnc,mhaberler/machinekit,EqAfrica/machinekit,RunningLight/machinekit,ianmcmahon/linuxcnc-mirror,RunningLight/machinekit,araisrobo/linuxcnc,ArcEye/MK-Qt5,unseenlaser/machinekit,araisrobo/machinekit,araisrobo/machinekit,bobvanderlinden/machinekit,cnc-club/linuxcnc,cdsteinkuehler/MachineKit,ianmcmahon/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,Cid427/machinekit,unseenlaser/linuxcnc,RunningLight/machinekit,aschiffler/linuxcnc,bmwiedemann/linuxcnc-mirror,cnc-club/linuxcnc,ianmcmahon/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,kinsamanka/machinekit,bobvanderlinden/machinekit,mhaberler/machinekit,unseenlaser/machinekit,EqAfrica/machinekit,araisrobo/linuxcnc,cnc-club/linuxcnc,ikcalB/linuxcnc-mirror,ArcEye/machinekit-testing,bobvanderlinden/machinekit,ArcEye/machinekit-testing,kinsamanka/machinekit,Cid427/machinekit,ArcEye/machinekit-testing,Cid427/machinekit,strahlex/machinekit,cdsteinkuehler/linuxcnc,cdsteinkuehler/MachineKit,kinsamanka/machinekit,araisrobo/machinekit,ArcEye/MK-Qt5,strahlex/machinekit,EqAfrica/machinekit,bmwiedemann/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,bobvanderlinden/machinekit,ArcEye/machinekit-testing,bobvanderlinden/machinekit,cdsteinkuehler/linuxcnc,ArcEye/machinekit-testing,bmwiedemann/linuxcnc-mirror,Cid427/machinekit,kinsamanka/machinekit,ArcEye/MK-Qt5,ArcEye/MK-Qt5,ianmcmahon/linuxcnc-mirror,unseenlaser/linuxcnc,kinsamanka/machinekit,EqAfrica/machinekit,cdsteinkuehler/MachineKit,mhaberler/machinekit,ianmcmahon/linuxcnc-mirror,kinsamanka/machinekit,mhaberler/machinekit,ArcEye/MK-Qt5,ArcEye/MK-Qt5,EqAfrica/machinekit,cnc-club/linuxcnc,RunningLight/machinekit,araisrobo/linuxcnc,ArcEye/machinekit-testing,narogon/linuxcnc,unseenlaser/machinekit,jaguarcat79/ILC-with-LinuxCNC,araisrobo/machinekit,Cid427/machinekit,jaguarcat79/ILC-with-LinuxCNC,ikcalB/linuxcnc-mirror,aschiffler/linuxcnc,Cid427/machinekit,cnc-club/linuxcnc,cdsteinkuehler/linuxcnc,unseenlaser/machinekit,bobvanderlinden/machinekit,cdsteinkuehler/linuxcnc,Cid427/machinekit,kinsamanka/machinekit,cnc-club/linuxcnc,mhaberler/machinekit,mhaberler/machinekit,kinsamanka/machinekit,araisrobo/linuxcnc,araisrobo/machinekit,bobvanderlinden/machinekit,strahlex/machinekit,ArcEye/machinekit-testing,strahlex/machinekit,bmwiedemann/linuxcnc-mirror,unseenlaser/machinekit,EqAfrica/machinekit,ikcalB/linuxcnc-mirror,RunningLight/machinekit,EqAfrica/machinekit,aschiffler/linuxcnc,narogon/linuxcnc,araisrobo/linuxcnc,Cid427/machinekit,unseenlaser/machinekit,jaguarcat79/ILC-with-LinuxCNC,ikcalB/linuxcnc-mirror,ianmcmahon/linuxcnc-mirror,araisrobo/machinekit,cdsteinkuehler/linuxcnc,unseenlaser/linuxcnc,RunningLight/machinekit,strahlex/machinekit,ianmcmahon/linuxcnc-mirror,ArcEye/MK-Qt5,RunningLight/machinekit,bmwiedemann/linuxcnc-mirror,ArcEye/MK-Qt5,araisrobo/machinekit,ikcalB/linuxcnc-mirror,unseenlaser/linuxcnc,mhaberler/machinekit,EqAfrica/machinekit,unseenlaser/linuxcnc,araisrobo/machinekit,mhaberler/machinekit,cdsteinkuehler/linuxcnc,aschiffler/linuxcnc