setup.py still declares Python 2.7 support #436

setup.py still declares Python 2.7 and 3.7+ (master, ecb4b74):

    python_requires=(
        ">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*,!=3.6.*"
    ),

The classifiers list 2, 2.7, 3.7, 3.8, 3.9, 3.10 and PyPy, and nothing after 3.10.

CI (main.yml, tests.yml) and tox.ini (envlist = py310,py311,py312,py313,py314) only test CPython 3.10-3.14.

Python 2.7 is already broken. Since 1.10.0 (e868dbe, #355), find_system_node() calls shutil.which, which 2.7 doesn't have, so --node=system and --prefer-system fail with AttributeError.

PR #434 changes the README to "Python 3 (CI tests CPython 3.10 through 3.14)". Once it is merged, the README and the package metadata will disagree.

To do:

• pick the minimum supported version and update python_requires
• update the classifiers to match it (they stop at 3.10)
• drop the Python 2 compatibility code in nodeenv.py:
  • the pipes.quote fallback for Python < 3.3
  • the try/except ImportError block with the py2 imports (ConfigParser, urllib2, urlparse, urllib.unquote, httplib) and the iteritems helper; urllib.request is still imported as urllib2
  • is_PY3 and to_utf8(), which returns the text unchanged on Python 3 (7 call sites)
  • the sys.version_info major check in build_node_from_src; PR fix: do not require python2 to build node from source #429 already rewrites it