release notes for python version 0.5.2

Author: MalteKurz

doc/release/release.rst

@@ -5,6 +5,10 @@ Release notes
 
 .. tabbed:: Python
 
+    **DoubleML 0.5.2**
+    - Fix / adapted unit tests which failed in the release of 0.5.1 to conda-forge
+      `#172 <https://github.com/DoubleML/doubleml-for-py/pull/172>`_
+
     **DoubleML 0.5.1**
 
     - Store estimated models for nuisance parameters