Add deprecation notice for Python 3.5

diff --git a/docs/releases/v6.1.0.rst b/docs/releases/v6.1.0.rst
index 02289ab5709e2f9ef01f8a0e8055e9293570e90d..0b7f5b23c7f677dad5bc5af0c1ac1ab5234f6fe0 100644 (file)
--- a/docs/releases/v6.1.0.rst
+++ b/docs/releases/v6.1.0.rst
@@ -4,6 +4,12 @@ What's new in Tornado 6.1.0
 Oct X, 2020
 -----------
 
+Deprecation notice
+~~~~~~~~~~~~~~~~~~
+
+- This is the last release of Tornado to support Python 3.5. Future versions
+  will require Python 3.6 or newer.
+
 General changes
 ~~~~~~~~~~~~~~~