Pin older setuptools for pip 9

tests/conftest.py

@@ -31,6 +31,8 @@
 # Version of pip to test micropipenv with
 # the default is the pip wheel bundled in virtualenv package
 MICROPIPENV_TEST_PIP_VERSION = os.getenv("MICROPIPENV_TEST_PIP_VERSION")
+# For some very old pips, we have to limit also setuptools version
+MICROPIPENV_TEST_SETUPTOOLS_VERSION = os.getenv("MICROPIPENV_TEST_SETUPTOOLS_VERSION")
 # pip version used in tests, assigned using pytest_configure
 PIP_VERSION = None
 
@@ -46,6 +48,9 @@ def _venv_install_pip(venv):
         else:
             venv.install(f"pip{MICROPIPENV_TEST_PIP_VERSION}")
 
+    if MICROPIPENV_TEST_SETUPTOOLS_VERSION is not None:
+        venv.install(f"setuptools{MICROPIPENV_TEST_SETUPTOOLS_VERSION}")
+
 
 def pytest_configure(config):
     """Configure tests before pytest collects tests."""

tox.ini

@@ -26,7 +26,10 @@ deps =
     tomli: tomli
 setenv =
     # platform-python-pip and python27-pip in RHEL8
-    pip90:  MICROPIPENV_TEST_PIP_VERSION = >=9.0,<10.0
+    # pip 9 seems not to be compatible with the latest setuptools
+    # so we are using the same version we have in RHEL 8
+    pip90: MICROPIPENV_TEST_PIP_VERSION = >=9.0,<10.0
+    pip90: MICROPIPENV_TEST_SETUPTOOLS_VERSION = <60
     # older version in Python 3.8 module
     pip192: MICROPIPENV_TEST_PIP_VERSION = >=19.2,<19.3
     # first version with manylinux2014 support, Python 3.8 module, Fedora 32