pinning at recipe level for python

Author: dwr-psandhu

conda.recipe/meta.yaml

@@ -22,7 +22,7 @@ requirements:
     - swig
 
   run:
-    - python >=3.5,<4.0
+    - {{ pin_compatible('python', lower_bound='3.5', upper_bound='4.0') }}
     - numpy  >=1.16
     - pandas >=0.23