Require a minimum setuptools version for Python 3.

When the `setuptools_dso` module is used having older versions of
setuptools installed, the `wheel` module (one of its dependencies)
sets up a handler for the root logging that writes to stdout
(https://github.com/pypa/wheel/issues/622).
This breaks the expected output of the programs, and thus the
wendeling.core tests.

However, if `setuptools.logging` is available, `wheel` will use it
instead and it won't set up a handler.
Thus, I added a explicit dependency to a version of setuptools above
60.2 for Python 3, as that is the first version that provides this
module.

setup.py

@@ -325,6 +325,7 @@ setup(
                         # setuptools_dso uses multiprocessing only on Python3, and only on systems where
                         # mp.get_start_method()!='fork', while geventmp does not work on windows.
                         'geventmp ; python_version>="3" and platform_system != "Windows" ',
+                        'setuptools >= 60.2 ; python_version>="3"',
                        ],
     extras_require   = extras_require,