Announce deprecation of Python 2.7 (#311)

Author: crwilcox

README.rst

@@ -26,6 +26,14 @@ For more information on setting up your Python development environment, please r
 
 .. _`Python Development Environment Setup Guide`: https://cloud.google.com/python/setup
 
+Supported Python Versions
+^^^^^^^^^^^^^^^^^^^^^^^^^
+Python >= 3.4
+
+Deprecated Python Versions
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+Python == 2.7. Python 2.7 support will be removed on January 1, 2020.
+
 Documentation
 -------------
 

setup.py

@@ -40,6 +40,7 @@
     packages=find_packages(exclude=('tests*', 'system_tests*')),
     namespace_packages=('google',),
     install_requires=DEPENDENCIES,
+    python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
     license='Apache 2.0',
     keywords='google auth oauth client',
     classifiers=[
@@ -49,6 +50,7 @@
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: Apache Software License',