qemu: disable Ceph when buildout with Python 2

Some Py2-SR like neoppod/stress-testing need Qemu but not Ceph.

Also note that the conditional [systemd-markupsafe-download] only works
if [systemd-python] uses the same Python as the one that runs buildout.

component/ceph/buildout.cfg

@@ -37,18 +37,14 @@ pyyaml = ${pyyaml-download:target}
 pyaml = ${pyaml-download:target}
 
 install =
-  import os
-  call([options['python'], '-m', 'venv', '--clear', location])
+  import os, sys
+  call([sys.executable, '-m', 'venv', '--clear', location])
   pip = os.path.join(location, 'bin', 'pip')
   call([pip, 'install', '--no-index', options['pyyaml'], options['pyaml']])
   call([pip, 'uninstall', '-y', 'pip', 'setuptools'])
   # selftest
-  python = os.path.join(location, 'bin', 'python3')
+  python = os.path.join(location, 'bin', 'python')
   call([python, '-c', 'import yaml'])
-python = ${python3:executable}
-
-[librbd-python:python3]
-python = ${buildout:executable}
 
 [librbd]
 # CEPH only for librbd

component/qemu-kvm/buildout.cfg

@@ -67,7 +67,7 @@ environment =
   PATH=${pkgconfig:location}/bin:${bzip2:location}/bin:%(PATH)s
   PKG_CONFIG_PATH=${glib:location}/lib/pkgconfig:${gnutls:location}/lib/pkgconfig:${gnutls:pkg-config-path}:${libpng:location}/lib/pkgconfig:${liburing:location}/lib/pkgconfig:${ncurses:location}/lib/pkgconfig:${pcre:location}/lib/pkgconfig:${pixman:location}/lib/pkgconfig${:PKG_CONFIG_PATH-rbd}
 
-[qemu:[int(q) for q in platform.libc_ver()[1].split(".")] < [2,25]]
+[qemu:python2 or [int(q) for q in platform.libc_ver()[1].split(".")] < [2,25]]
 configure-rbd =
 CFLAGS-rbd =
 LDFLAGS-rbd =

component/systemd/buildout.cfg

@@ -38,18 +38,14 @@ markupsafe = ${systemd-markupsafe-download:target}
 jinja2 = ${systemd-jinja2-download:target}
 
 install =
-  import os
-  call([options['python'], '-m', 'venv', '--clear', location])
+  import os, sys
+  call([sys.executable, '-m', 'venv', '--clear', location])
   pip = os.path.join(location, 'bin', 'pip')
   call([pip, 'install', '--no-index', options['markupsafe'], options['jinja2']])
   call([pip, 'uninstall', '-y', 'pip', 'setuptools'])
   # selftest
-  python = os.path.join(location, 'bin', 'python3')
+  python = os.path.join(location, 'bin', 'python')
   call([python, '-c', 'import jinja2'])
-python = ${python3:executable}
-
-[systemd-python:python3]
-python = ${buildout:executable}
 
 [systemd]
 recipe = slapos.recipe.build