hash collisions ValueError -> AssertionError

Author: jreback

pandas/src/hashtable_class_helper.pxi.in

@@ -868,11 +868,11 @@ cdef class MultiIndexHashTable(HashTable):
             ndarray[int64_t] alocs
 
         alocs = np.asarray(locs)
-        if (alocs!=-1).all():
+        if (alocs != -1).all():
 
             result = self.mi.take(locs)
             if not result.equals(mi):
-                raise ValueError("hash collision alert")
+                raise AssertionError("hash collision alert")
 
     def __contains__(self, object key):
         cdef: