added schema_test to test for failure to write schema graph when reopened (second time)
added schema_test to test for failure to write schema graph when reopened (second time)

ctb/pygr,ctb/pygr,ctb/pygr,RitwikGupta/pygr,RitwikGupta/pygr,ctb/pygr,GenDataPro/pygr,cjlee112/pygr,cjlee112/pygr,ctb/pygr,cjlee112/pygr,RitwikGupta/pygr,theoryno3/pygr,theoryno3/pygr,GenDataPro/pygr,cjlee112/pygr,theoryno3/pygr,GenDataPro/pygr