DOC deprecation of **kwargs in neighbors per 0.18

Author: larsmans

doc/whats_new.rst

@@ -48,6 +48,17 @@ Bug fixes
     - The ``transform`` of :class:`lda.LDA` now projects the input on the most
       discriminant directions. By Martin Billinger.
 
+    - Nearest neighbors estimators now reliably work inside ``GridSearchCV``,
+      thanks to Nikolay Mayorov.
+
+
+API changes summary
+-------------------
+
+    - Nearest neighbors estimators used to take arbitrary keyword arguments
+      and pass these to their distance metric. This will no longer be supported
+      in scikit-learn 0.18; use the ``metric_params`` argument instead.
+
 
 .. _changes_0_15:
 

sklearn/neighbors/base.py

@@ -101,8 +101,9 @@ def _init_params(self, n_neighbors=None, radius=None,
                      p=2, metric_params=None, **kwargs):
         if kwargs:
             warnings.warn("Passing additional arguments to the metric "
-                          "function as **kwargs is deprecated. "
-                          "Use metric_params dict instead.",
+                          "function as **kwargs is deprecated "
+                          "and will no longer be supported in 0.18. "
+                          "Use metric_params instead.",
                           DeprecationWarning, stacklevel=3)
             if metric_params is None:
                 metric_params = {}