nose: clean up, support Python 3.10. (#8825)

Due to changes in setuptools, we need to run 2to3 ourselves.
While we're at it, lets apply relevant patches from Debian.

https://salsa.debian.org/python-team/packages/nose/

dev-python/nose/patches/debian/sphinx-class-directives.diff

@@ -0,0 +1,39 @@
+From: Dmitry Shachnev <mitya57@debian.org>
+Date: Thu, 25 Jun 2020 11:58:34 +0300
+Subject: Use class-based directives to fix build with Sphinx 3.x
+
+---
+ nose/sphinx/pluginopts.py | 15 +++++++++++----
+ 1 file changed, 11 insertions(+), 4 deletions(-)
+
+diff --git a/nose/sphinx/pluginopts.py b/nose/sphinx/pluginopts.py
+index d2b284a..033297b 100644
+--- a/nose/sphinx/pluginopts.py
++++ b/nose/sphinx/pluginopts.py
+@@ -34,7 +34,7 @@ import os
+ try:
+     from docutils import nodes, utils
+     from docutils.statemachine import ViewList
+-    from docutils.parsers.rst import directives
++    from docutils.parsers.rst import convert_directive_function, directives
+ except ImportError:
+     pass # won't run anyway
+ 
+@@ -183,7 +183,14 @@ class Opt(object):
+ 
+     
+ def setup(app):
++    autoplugin_directive.content = True
++    autoplugin_directive.arguments = (1, 0, True)
++    autoplugin_directive.options = {'plugin': directives.unchanged}
+     app.add_directive('autoplugin',
+-                      autoplugin_directive, 1, (1, 0, 1),
+-                      plugin=directives.unchanged)
+-    app.add_directive('autohelp', autohelp_directive, 0, (0, 0, 1))
++                      convert_directive_function(autoplugin_directive))
++
++    autohelp_directive.content = False
++    autohelp_directive.arguments = (0, 0, True)
++    autohelp_directive.options = {}
++    app.add_directive('autohelp',
++                      convert_directive_function(autohelp_directive))