typing_extensions: Drop support for Python 3.4 & 3.5 (#881)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

typing_extensions/setup.cfg

@@ -1,2 +1,5 @@
 [metadata]
 license-file = LICENSE
+
+[options]
+python_version = >=3.6

typing_extensions/setup.py

@@ -4,31 +4,25 @@
 import sys
 from setuptools import setup
 
-if sys.version_info < (2, 7, 0) or (3, 0, 0) <= sys.version_info < (3, 4, 0):
-    sys.stderr.write('ERROR: You need Python 2.7 or 3.4+ '
-                     'to install the typing package.\n')
+if sys.version_info < (2, 7, 0) or (3, 0, 0) <= sys.version_info < (3, 6, 0):
+    sys.stderr.write('ERROR: You need Python 2.7 or 3.6+ '
+                     'to install typing_extensions.\n')
     exit(1)
 
 version = '3.10.0.2'
-description = 'Backported and Experimental Type Hints for Python 3.5+'
+description = 'Backported and Experimental Type Hints for Python 3.6+'
 long_description = '''\
 Typing Extensions -- Backported and Experimental Type Hints for Python
 
 The ``typing`` module was added to the standard library in Python 3.5, but
 many new features have been added to the module since then.
-This means users of Python 3.5 - 3.6 who are unable to upgrade will not be
+This means users of older Python versions who are unable to upgrade will not be
 able to take advantage of new types added to the ``typing`` module, such as
 ``typing.Protocol`` or ``typing.TypedDict``.
 
 The ``typing_extensions`` module contains backports of these changes.
 Experimental types that will eventually be added to the ``typing``
-module are also included in ``typing_extensions``, such as
-``typing.ParamSpec`` and ``typing.TypeGuard``.
-
-Users of Python versions before 3.5 should install and use
-the ``typing`` module from PyPI instead of using this one, unless specifically
-writing code that must be compatible with multiple Python versions or requires
-experimental types.
+module are also included in ``typing_extensions``.
 '''
 
 classifiers = [
@@ -38,8 +32,6 @@
     'License :: OSI Approved :: Python Software Foundation License',
     'Operating System :: OS Independent',
     'Programming Language :: Python :: 2.7',
-    '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',