component/python3: share the python 3.x parts

component/python3/buildout.cfg

@@ -21,12 +21,10 @@ parts =
 
 [python3-common]
 recipe = slapos.recipe.cmmi
+shared = true
 package_version_suffix =
 
-# This is actually the default setting for prefix, but we can't use it in
-# other settings in this part if we don't set it explicitly here.
-prefix = ${buildout:parts-directory}/${:_buildout_section_name_}
-executable = ${:prefix}/bin/${:_buildout_section_name_}
+executable = @@LOCATION@@/bin/${:_buildout_section_name_}
 
 patch-options = -p1
 patches =
@@ -71,7 +69,6 @@ package_version = 3.7.2
 md5sum = df6ec36011808205beda239c72f947cb
 patch-options =
 patches =
-executable = @@LOCATION@@/bin/python3.7
 environment =
   PATH=${gcc-8.2:location}/bin::${xz-utils:location}/bin:%(PATH)s
   CPPFLAGS=-I${zlib:location}/include -I${xz-utils:location}/include -I${readline:location}/include -I${libexpat:location}/include -I${libffi:location}/include -I${ncurses:location}/include -I${ncurses:location}/include/ncursesw -I${bzip2:location}/include  -I${gdbm:location}/include -I${openssl:location}/include -I${sqlite3:location}/include -I${gettext:location}/include