Fix tests for IPython.testing

IPython/testing/plugin/show_refs.py

@@ -15,6 +15,6 b" if __name__ == '__main__':"
    c = C()
 
    c_refs = gc.get_referrers(c)
-   ref_ids = map(id,c_refs)
+   ref_ids = list(map(id,c_refs))
 
-   print('c referrers:',map(type,c_refs))
+   print('c referrers:',list(map(type,c_refs)))