TST: fix test errors on Python 3, close #1550

Author: wesm

pandas/sparse/frame.py

@@ -276,7 +276,7 @@ def _set_item(self, key, value):
             self._insert_column(key)
 
     def _insert_column(self, key):
-        self.columns = Index(np.concatenate((self.columns, [key])))
+        self.columns = self.columns.insert(len(self.columns), key)
 
     def __delitem__(self, key):
         """

pandas/stats/tests/test_fama_macbeth.py

@@ -36,7 +36,7 @@ def checkFamaMacBethExtended(self, window_type, x, y, **kwds):
             end = index[i + window - 1]
 
             x2 = {}
-            for k, v in x.iteritems():
+            for k, v in x.iterkv():
                 x2[k] = v.truncate(start, end)
             y2 = y.truncate(start, end)
 

pandas/stats/tests/test_ols.py

@@ -490,7 +490,7 @@ def test_wls_panel(self):
 
         stack_y = y.stack()
         stack_x = DataFrame(dict((k, v.stack())
-                                  for k, v in x.iteritems()))
+                                  for k, v in x.iterkv()))
 
         weights = x.std('items')
         stack_weights = weights.stack()