Use SETUPTOOLS_USE_DISTUTILS=stdlib for global pip installs

A new setuptools release has changed the way pip installs are done,
see [0]. With this change we switch back to using the distro
method for global pip installs.

Temporarily make grenade jobs non-voting in order to allow this
patch to be backported.

[0] http://lists.openstack.org/pipermail/openstack-discuss/2020-August/016905.html

Change-Id: I5d8aa0e58e0409c54451b51de5eb70ba9a68d849

.zuul.yaml

@@ -705,10 +705,12 @@
             voting: false
             irrelevant-files: *dsvm-irrelevant-files
         - grenade:
+            voting: false
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
         - neutron-grenade-multinode:
+            voting: false
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
@@ -750,18 +752,18 @@
         - devstack-multinode
         - devstack-unit-tests
         - openstack-tox-bashate
-        - neutron-grenade-multinode:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^doc/.*$
+        # - neutron-grenade-multinode:
+        #     irrelevant-files:
+        #       - ^.*\.rst$
+        #       - ^doc/.*$
         - neutron-tempest-linuxbridge:
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
-        - grenade:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^doc/.*$
+        # - grenade:
+        #     irrelevant-files:
+        #       - ^.*\.rst$
+        #       - ^doc/.*$
         - openstacksdk-functional-devstack:
             irrelevant-files:
               - ^.*\.rst$

inc/python

@@ -170,7 +170,13 @@ function pip_install {
         local sudo_pip="env"
     else
         local cmd_pip="python$PYTHON3_VERSION -m pip"
-        local sudo_pip="sudo -H LC_ALL=en_US.UTF-8"
+        # See
+        #  https://github.com/pypa/setuptools/issues/2232
+        #  http://lists.openstack.org/pipermail/openstack-discuss/2020-August/016905.html
+        # this makes setuptools >=50 use the platform distutils.
+        # We only want to do this on global pip installs, not if
+        # installing in a virtualenv
+        local sudo_pip="sudo -H LC_ALL=en_US.UTF-8 SETUPTOOLS_USE_DISTUTILS=stdlib "
         echo "Using python $PYTHON3_VERSION to install $package_dir"
     fi