Downgrade pip, wheel and setuptools in python2 SRs

When using slapos.reboostrap to re-launch buildout with the version
of Python that was just installed, zc.buildout and its dependencies
are reinstalled for the new Python with the same egg versions. Thus
SRs which install Python 2 need to use Python-2-compatible versions
of setuptools, pip and wheel all along.

For this stack/slapos-py2.cfg is introduced.

software/backupserver/software.cfg

@@ -15,6 +15,9 @@ extends =
   ../../stack/slapos.cfg
   ../../stack/monitor/buildout.cfg
 
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg
+
 parts =
   dcron
   logrotate
@@ -27,9 +30,6 @@ parts =
   template-crontab-line
   slapos-cookbook
 
-[python]
-part = python2.7
-
 [rssgen-eggs]
 recipe = zc.recipe.egg
 interpreter = python-${:_buildout_section_name_}

software/beremiz-ide/software.cfg

@@ -28,6 +28,9 @@ extends =
   ../../stack/nxdtest.cfg
   ./buildout.hash.cfg
 
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg
+
 parts +=
   slapos-cookbook
   beremiz-eggs
@@ -41,10 +44,6 @@ parts +=
 # Always build GCC for Fortran (see openblas).
 max_version = 0
 
-[python]
-# Beremiz works with python2.7 for now, the code is not yet upgraded for python3
-part = python2.7
-
 [open62541]
 # Beremiz need it to be in folder parts/open62541
 # as Beremiz search for open62541 to BEREMIZ_PATH/../open62541

software/dream/software.cfg

@@ -6,6 +6,10 @@ extends =
   ../../component/manpy/buildout.cfg
   ../../stack/monitor/buildout.cfg
   ./buildout.hash.cfg
+
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg
+
 parts =
   slapos-cookbook
   manpy
@@ -21,9 +25,6 @@ max_version = 0
 # also use old gcc version for old scipy version used in python2
 part = gcc-8.5
 
-[python]
-part = python2.7
-
 [dream-repository.git]
 revision = f3bcf115741886835df8c0ca0fdbf510d77d8db8
 

software/re6stnet/software.cfg

@@ -13,13 +13,13 @@ extends =
 # Monitoring stack (keep on bottom)
   ../../stack/monitor/buildout.cfg
 
+# Python2 versions for buildout (keep bottom-most)
+  ../../stack/slapos-py2.cfg
+
 parts +=
   slapos-cookbook
   template
 
-[python]
-part = python2.7
-
 [re6stnet-repository]
 recipe = slapos.recipe.build:gitclone
 repository = https://lab.nexedi.com/nexedi/re6stnet.git

stack/erp5/buildout.cfg

@@ -68,6 +68,9 @@ extends =
   ../../software/neoppod/software-common.cfg
 # keep neoppod extends last
 
+# python2
+  ../slapos-py2.cfg
+
 parts +=
   erp5-util-develop
   slapos-cookbook

stack/slapos-py2.cfg

+[buildout]
+extends = slapos.cfg
+
+[python]
+part = python2.7
+
+# Use Python2-compatible versions of zc.buildout dependencies from the start.
+# These versions must be pinned unconditionally because slapos.rebootstrap
+# will necessarily keep the same versions of zc.buildout and dependencies
+# with the new Python. This is an intrisic limitation of slapos.rebootstrap.
+[versions]
+setuptools = 44.1.1
+pip = 20.3.4
+# Avoid https://github.com/pypa/wheel/issues/331
+wheel = 0.33.6

stack/slapos.cfg

@@ -413,7 +413,6 @@ statsmodels = 0.11.1
 traitlets = 4.3.3
 uritemplate = 3.0.0
 Werkzeug = 1.0.1
-wheel = 0.35.1:whl
 zipp = 1.2.0:whl