[PATCH] python: pin setuptools below v60.0.0

[John Snow <jsnow@redhat.com>]

setuptools is a package that replaces the python stdlib 'distutils'. It
is generally installed by all venv-creating tools "by default". It isn't
actually needed at runtime for the qemu package, so our own setup.cfg
does not mention it as a dependency.

However, tox will create virtual environments that include it, and will
upgrade it to the very latest version. the 'venv' tool will also include
whichever version your host system happens to have.

Unfortunately, setuptools version 60.0.0 and above include a hack to
forcibly overwrite python's built-in distutils. The pylint tool that we
use to run code analysis checks on this package relies on distutils and
suffers regressions when setuptools >= 60.0.0 is present at all, see
https://github.com/PyCQA/pylint/issues/5704

Instruct tox and the 'check-dev' targets to avoid setuptools packages
that are too new, for now. Pipenv is unaffected, because setuptools 60
does not offer Python 3.6 support, and our pipenv config is pinned
against Python 3.6.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 python/Makefile  | 2 ++
 python/setup.cfg | 1 +
 2 files changed, 3 insertions(+)

diff --git a/python/Makefile b/python/Makefile
index 3334311362..949c472624 100644
--- a/python/Makefile
+++ b/python/Makefile
@@ -68,6 +68,8 @@ $(QEMU_VENV_DIR) $(QEMU_VENV_DIR)/bin/activate: setup.cfg
 		echo "ACTIVATE $(QEMU_VENV_DIR)";		\
 		. $(QEMU_VENV_DIR)/bin/activate;		\
 		echo "INSTALL qemu[devel] $(QEMU_VENV_DIR)";	\
+		pip install --disable-pip-version-check		\
+			"setuptools<60.0.0" 1>/dev/null;	\
 		make develop 1>/dev/null;			\
 	)
 	@touch $(QEMU_VENV_DIR)
diff --git a/python/setup.cfg b/python/setup.cfg
index 417e937839..aa238d8bc9 100644
--- a/python/setup.cfg
+++ b/python/setup.cfg
@@ -163,6 +163,7 @@ deps =
     .[devel]
     .[fuse]  # Workaround to trigger tox venv rebuild
     .[tui]   # Workaround to trigger tox venv rebuild
+    setuptools < 60  # Workaround, please see commit msg.
 commands =
     make check
 
-- 
2.31.1