Document Python 2 deprecation (#6910)

Author: crwilcox

packages/google-cloud-firestore/README.rst

@@ -53,6 +53,15 @@ dependencies.
 .. _`virtualenv`: https://virtualenv.pypa.io/en/latest/
 
 
+Supported Python Versions
+^^^^^^^^^^^^^^^^^^^^^^^^^
+Python >= 3.4
+
+Deprecated Python Versions
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+Python == 2.7. Python 2.7 support will be removed on January 1, 2020.
+
+
 Mac/Linux
 ^^^^^^^^^
 

packages/google-cloud-firestore/setup.py

@@ -77,6 +77,7 @@
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
         'Operating System :: OS Independent',
         'Topic :: Internet',
     ],
@@ -85,6 +86,7 @@
     namespace_packages=namespaces,
     install_requires=dependencies,
     extras_require=extras,
+    python_requires='>=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
     include_package_data=True,
     zip_safe=False,
 )