py2/py3: install each python's 2to3.

software/erp5/software-py3.cfg

@@ -9,3 +9,7 @@ part = python3
 repository = https://lab.nexedi.com/nexedi/erp5.git
 branch = zope4py3
 develop = true
+
+[template-zope]
+link-binary +=
+  ${python3:location}/bin/2to3

software/erp5/software.cfg

 [buildout]
 extends =
   ../../stack/erp5/buildout.cfg
+
+[template-zope]
+link-binary +=
+  ${python2.7:location}/bin/2to3

stack/erp5/buildout.cfg

@@ -271,7 +271,6 @@ link-binary =
   ${poppler:location}/bin/pdfinfo
   ${poppler:location}/bin/pdftohtml
   ${poppler:location}/bin/pdftotext
-  ${python2.7:location}/bin/2to3
   ${sed:location}/bin/sed
   ${tesseract:location}/bin/tesseract
   ${w3m:location}/bin/w3m