Document Python 2 deprecation (#6910)


diff --git a/README.rst b/README.rst
index b475267..f0caaaf 100644
--- a/README.rst
+++ b/README.rst
@@ -12,3 +12,12 @@
 .. |versions| image:: https://img.shields.io/pypi/pyversions/google-api_core.svg
    :target: https://pypi.org/project/google-api_core/
 .. _documentation: https://googlecloudplatform.github.io/google-cloud-python/latest/core/
+
+
+Supported Python Versions
+-------------------------
+Python >= 3.4
+
+Deprecated Python Versions
+--------------------------
+Python == 2.7. Python 2.7 support will be removed on January 1, 2020.
\ No newline at end of file