Throw NotReducableLearnblockWarning.

cml/domain/complexity_reduction.py

 from cml.shared.parameter import PROTOCOL_LEVEL
+from cml.shared.errors import NotReducableLearnblockWarning
 
 
 __all__ = (
@@ -40,11 +41,11 @@ class FeatureSelector:
             if self._to_many_features(learnblock.feature_count) \
                     or self.settings.max_model_reduction:
                 past_feature_number = learnblock.feature_count
-
                 if self._filter_method_criteria(learnblock.feature_count,
                                                 learnblock.rows):
                     remove_features = self.filtering(learnblock)
                     learnblock.drop_columns_by_index(remove_features)
+
                 else:
                     remove_features = self.embedding(learnblock)
                     learnblock.drop_columns_by_index(remove_features)
@@ -56,7 +57,7 @@ class FeatureSelector:
 
                 elif past_feature_number == learnblock.feature_count \
                         and self._to_many_features(learnblock.feature_count):
-                    raise ValueError("Can't reduce learnblock")
+                    raise NotReducableLearnblockWarning()
                 else:
                     continue