slapos-node package: use python3.7 for now

python3.8 can run only buildout versions greater than 2.7.1+slapos019
which restrict a lot the number of SR buildable by slapos.

See merge request nexedi/slapos!1240

component/slapos/obs.cfg

@@ -31,6 +31,7 @@ init +=
   assert buildout['directory'] == buildout['destdir'] + buildout['rootdir'], (
     "Buildout MUST BE launched in destdir/rootdir (currently launched in %s but should be launched in %s)" %
     (buildout['directory'], buildout['destdir'] + buildout['rootdir']))
+part = python3.7
 
 [python3-common]
 configure-options +=
@@ -85,8 +86,8 @@ pre-configure =
   sed -i 's#/opt/slapos/parts/dbus/lib/libdbus-1.la#${dbus:location}/lib/libdbus-1.la#' ${dbus-glib:location}/lib/libdbus-glib-1.la
 environment +=
   LD_LIBRARY_PATH=${dbus:location}/lib
-  PYTHON_INCLUDES=-I${python:location}/include/python${python:version}
-  PYTHON_LIBS=-L${python:location}/lib -lpython${python:version} -lpthread -ldl -lutil -lm
+  PYTHON_INCLUDES=-I${python:location}/include/python${python:version}m
+  PYTHON_LIBS=-L${python:location}/lib -lpython${python:version}m -lpthread -ldl -lutil -lm
 post-install =
   sed -i 's#${dbus:location}/lib/libdbus-1.la#/opt/slapos/parts/dbus/lib/libdbus-1.la#' ${dbus-glib:location}/lib/libdbus-glib-1.la