build,python: Build Python bindings without distutils

* m4/python.m4: Add python3.12 and 3.11 as valid interpreters, remove
EOL 3.4, 3.5, 3.7 (keep 3.6 because some distributions still ship and
maintain it).
* lang/python/Makefile.am (clean-local): Remove dist and gpg.egg-info
created by Python 3.9+ on make install.
* lang/python/setup.py.in: switch from distutils to setuptools where
possible, remove obsolete and deprecated -py3 option of swig, add
classifiers up to 3.12, remove 3.4, 3.5, 3.7.
* lang/python/doc/src/gpgme-python-howto.org: replace distutils with
setuptools
* lang/python/examples/howto/advanced/cython/setup.py: replace distutils
with setuptools
--

This fixes building the Python bindings for Python 3.12 where distutils
has been removed.

Based on D545

lang/python/Makefile.am

@@ -80,7 +80,7 @@ CLEANFILES = copystamp \
 # 'make distclean' clears the write bit, breaking rm -rf.  Fix the
 # permissions.
 clean-local:
-	rm -rf -- build
+	rm -rf -- build dist gpg.egg-info
 	for PYTHON in $(PYTHONS); do \
 	  find "$$(basename "$${PYTHON}")-gpg" -type d ! -perm -200 -exec chmod u+w {} ';' ; \
 	  rm -rf -- "$$(basename "$${PYTHON}")-gpg" ; \

lang/python/doc/src/gpgme-python-howto.org

@@ -2945,7 +2945,7 @@ Save that into a file called =keycount.pyx= and then create a
 =setup.py= file which contains this:
 
 #+BEGIN_SRC python -i
-from distutils.core import setup
+from setuptools import setup
 from Cython.Build import cythonize
 
 setup(

lang/python/examples/howto/advanced/cython/setup.py

@@ -1,4 +1,4 @@
-from distutils.core import setup
+from setuptools import setup
 from Cython.Build import cythonize
 
 setup(

lang/python/setup.py.in

@@ -18,8 +18,12 @@
 #    License along with this library; if not, write to the Free Software
 #    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 
-from distutils.core import setup, Extension
-from distutils.command.build import build
+try:
+    from setuptools import setup, Extension
+    from setuptools.command.build import build
+except ImportError:
+    from distutils.core import setup, Extension
+    from distutils.command.build import build
 
 import glob
 import os
@@ -225,9 +229,8 @@ class BuildExtFirstHack(build):
         build.run(self)
 
 
-py3 = [] if sys.version_info.major < 3 else ['-py3']
 swig_sources = []
-swig_opts = ['-threads'] + py3 + extra_swig_opts
+swig_opts = ['-threads'] + extra_swig_opts
 swige = Extension(
     'gpg._gpgme',
     sources=swig_sources,
@@ -282,10 +285,12 @@ GPGME and these bindings is available here:
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
-        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
+        'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12',
         'Operating System :: POSIX',
         'Operating System :: Microsoft :: Windows',
         'Topic :: Communications :: Email',

m4/python.m4

@@ -36,12 +36,12 @@
 # numbers and dots only.
 AC_DEFUN([AM_PATH_PYTHON],
  [
-  dnl Find a Python interpreter.  Python versions prior to 2.7 are not
-  dnl supported. Python 3.0 through to Python 3.3 are also not supported.
+  dnl Find a Python interpreter.  Python versions prior to 3.8 are
+  dnl end-of-life and not supported, with the exception of 2.7 and 3.6.
   m4_define_default([_AM_PYTHON_INTERPRETER_LIST],
 [python2 python2.7 dnl
  python dnl
- python3 python3.10 python3.9 python3.8 python3.7 python3.6 python3.5 python3.4
+ python3 python3.12 python3.11 python3.10 python3.9 python3.8 python3.6
  ])
 
   AC_ARG_VAR([PYTHON], [the Python interpreter])