diff -Naur astropy/astropy/io/misc/tests/test_hdf5.py astropy.new/astropy/io/misc/tests/test_hdf5.py
--- astropy/astropy/io/misc/tests/test_hdf5.py	2017-09-08 16:43:52.000000000 +0200
+++ astropy.new/astropy/io/misc/tests/test_hdf5.py	2017-10-08 11:18:36.312982468 +0200
@@ -413,7 +413,8 @@
     assert len(w) == 1
     assert str(w[0].message).startswith(
         "Attributes could not be written to the output HDF5 "
-        "file: Unable to create attribute (Object header message is too large)")
+        "file: Unable to create attribute ")
+    assert "bject header message is too large" in str(w[0].message)
 
 
 @pytest.mark.skipif('not HAS_H5PY')