Skip tests if the file mapping file cannot be fetched.

Lib/test/test_multibytecodec_support.py

@@ -276,7 +276,10 @@ class TestBase_Mapping(unittest.TestCase):
 
     def __init__(self, *args, **kw):
         unittest.TestCase.__init__(self, *args, **kw)
-        self.open_mapping_file() # test it to report the error early
+        try:
+            self.open_mapping_file() # test it to report the error early
+        except IOError:
+            raise test_support.TestSkipped("Could not retrieve "+self.mapfileurl)
 
     def open_mapping_file(self):
         return test_support.open_urlresource(self.mapfileurl)