Add some debugging

Author: Guillaume Lemaitre

imblearn/base.py

@@ -20,7 +20,7 @@
 from six import string_types
 
 
-warnings.simplefilter('always', category=UserWarning)
+warnings.simplefilter('always', UserWarning)
 
 
 class SamplerMixin(six.with_metaclass(ABCMeta, BaseEstimator)):
@@ -88,6 +88,9 @@ def fit(self, X, y):
         # if uniques.size == 1:
         #     raise RuntimeError("Only one class detected, aborting...")
         # Raise a warning for the moment to be compatible with BaseEstimator
+        self.logger.debug('The number of classes is %s', np.unique(y).size)
+        self.logger.debug('Shall we raise a warning: %s',
+                          np.unique(y).size == 1)
         if np.unique(y).size == 1:
             warnings.warn('Only one class detected, something will get wrong')