BUG: Using numpy all() method

Author: aschade

pandas/core/generic.py

@@ -2909,7 +2909,7 @@ def _drop_axis(self, labels, axis, level=None, errors='raise'):
             else:
                 indexer = ~axis.isin(labels)
 
-            if all(indexer) and errors == 'raise':
+            if indexer.all() and errors == 'raise':
                 raise ValueError('{} not found in axis'.format(labels))
 
             slicer = [slice(None)] * self.ndim