Start new release cycle (#672)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index faf781a..db6cadd 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -5,6 +5,31 @@
 The third digit is only for regressions.
 
 
+17.3.0 (UNRELEASED)
+-------------------
+
+
+Backward-incompatible changes:
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+*none*
+
+
+Deprecations:
+^^^^^^^^^^^^^
+
+*none*
+
+
+Changes:
+^^^^^^^^
+
+*none*
+
+
+----
+
+
 17.2.0 (2017-07-20)
 -------------------