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/python3-conf-py.diff

@@ -0,0 +1,23 @@
+From: Dmitry Shachnev <mitya57@debian.org>
+Date: Sat, 30 Oct 2021 20:44:42 +0300
+Subject: Fix syntax in doc/conf.py for Python 3
+
+---
+ doc/conf.py | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/doc/conf.py b/doc/conf.py
+index cccfd95..dab07bf 100644
+--- a/doc/conf.py
++++ b/doc/conf.py
+@@ -217,8 +217,8 @@ html_theme = 'default'
+ # Grouping the document tree into LaTeX files. List of tuples
+ # (source start file, target name, title, author, document class [howto/manual]).
+ latex_documents = [
+-  ('index', 'nose.tex', ur'nose Documentation',
+-   ur'Jason Pellerin', 'manual'),
++  ('index', 'nose.tex', u'nose Documentation',
++   u'Jason Pellerin', 'manual'),
+ ]
+ 
+ # The name of an image file (relative to this directory) to place at the top of