patching in siegfried's xsd assertion for now #881

Job	Run time
Linux (Debug, SHARED_LIBS=OFF)	1m 59s
Linux (Release, SHARED_LIBS=ON)	1m 54s
Linux (Release, SHARED_LIBS=OFF)	2m 14s
Linux (Debug, SHARED_LIBS=ON)	1m 58s
	8m 5s

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