Add support for Python 3.10

and remove support for Python 3.6.

issue11048
review364451002

setup.py

@@ -138,16 +138,16 @@ setup(name=name,
         'Natural Language :: Turkish',
         'Operating System :: OS Independent',
         'Programming Language :: Python :: 3',
-        '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 :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Office/Business',
         ],
     license='GPL-3',
-    python_requires='>=3.6',
+    python_requires='>=3.7',
     install_requires=requires,
     dependency_links=dependency_links,
     zip_safe=False,