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.

It is also used to move all

```
[openssl]
<= openssl-1.1
```

from individual Python2 SRs to a common place.

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
@@ -27,12 +30,6 @@ parts =
   template-crontab-line
   slapos-cookbook
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [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
@@ -41,13 +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
-
-[openssl]
-<= openssl-1.1
-
 [open62541]
 # Beremiz need it to be in folder parts/open62541
 # as Beremiz search for open62541 to BEREMIZ_PATH/../open62541

software/beremiz-runtime/software.cfg

@@ -11,6 +11,9 @@ extends =
   ../../stack/monitor/buildout.cfg
   ../../stack/slapos.cfg
 
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg
+
 parts =
   beremiz-source
   slapos-cookbook
@@ -19,12 +22,6 @@ parts =
   matiec
   open62541
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [gcc]
 # we want this SR to use a fixed gcc (so that we have the same gcc as open62541 component)
 max_version = 0

software/build-rina/software.cfg

@@ -3,17 +3,15 @@ extends =
   ../../stack/slapos.cfg
   ../../component/vm-img/debian.cfg
   ../../component/rina-tools/buildout.cfg
+
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg
+
 parts =
   slapos-cookbook
   template
 download-cache = ${:directory}/download-cache
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [template]
 recipe = slapos.recipe.template:jinja2
 # XXX: "template.cfg" is hardcoded in instanciation recipe

software/buildout-testing/runTestSuite.in

@@ -114,6 +114,7 @@ zope.testrunner = 5.2
 recipe = zc.recipe.egg
 eggs =
   ${:recipe}
+  zc.buildout[test]
   zope.testing
   zope.testrunner
 scripts =

software/buildout-testing/software-py2.cfg

@@ -2,8 +2,5 @@
 extends =
   software.cfg
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
+# Python2 versions for buildout (keep last)
+  ../../stack/slapos-py2.cfg

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
@@ -21,12 +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
-
-[openssl]
-<= openssl-1.1
-
 [dream-repository.git]
 revision = f3bcf115741886835df8c0ca0fdbf510d77d8db8
 

software/hellorina/software.cfg

@@ -2,16 +2,14 @@
 extends =
     ../../stack/slapos.cfg
     ../../component/rina-tools/buildout.cfg
+
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
+
 parts =
     slapos-cookbook
     template
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [file]
 # For old GCC like 4.9.2 on Debian 8.
 # XXX: This should be moved to component/rina-tools/buildout.cfg, next to where

software/neoppod/software-common.cfg

@@ -23,6 +23,9 @@ extends =
     ../../component/ZEO/buildout.cfg
     ../../component/zodbtools/buildout.cfg
 
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
+
 parts =
 # keep neoppod first so that ZODB is built correctly,
 # before any other section that would depend on it
@@ -30,12 +33,6 @@ parts =
     neoppod
     slapos-cookbook
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [gcc:python2]
 # use old gcc version for old scipy version used in python2
 part = gcc-8.5

software/neotest/software.cfg

@@ -19,6 +19,8 @@ extends =
     ../../component/pygolang/buildout.cfg
     ../../stack/nxdtest.cfg
 
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
 
 parts =
     gowork
@@ -47,12 +49,6 @@ parts =
     slapos-cookbook
     instance.cfg
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [neo]
 <= go-git-package
 go.importpath = lab.nexedi.com/kirr/neo

software/re6stnet/software.cfg

@@ -13,16 +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
-
-[openssl]
-<= openssl-1.1
-
 [re6stnet-repository]
 recipe = slapos.recipe.build:gitclone
 repository = https://lab.nexedi.com/nexedi/re6stnet.git

software/slapos-testing/software-py2.cfg

@@ -2,11 +2,8 @@
 extends =
   software.cfg
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
 
 [extra-eggs]
 eggs +=

software/tsn-demo/software.cfg

@@ -6,18 +6,15 @@ extends =
   ../../component/tsn-rt-measures/buildout.cfg
   ../../component/util-linux/buildout.cfg
 
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
+
 parts =
   slapos-cookbook
   eggs
   util-linux
   template
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 # eggs for instance-rsn-client.cfg
 [eggs]
 recipe  = zc.recipe.egg

software/zabbix-agent/software.cfg

@@ -6,16 +6,13 @@ extends =
   ../../component/zabbix/buildout.cfg
   ../../stack/slapos.cfg
 
+# Python2 versions for buildout (keep last)
+    ../../stack/slapos-py2.cfg
+
 parts =
   slapos-cookbook
   template
 
-[python]
-part = python2.7
-
-[openssl]
-<= openssl-1.1
-
 [template]
 # Default template for the instance.
 recipe = slapos.recipe.template

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
+
+[openssl]
+<= openssl-1.1
+
+# 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