Update stevedore from 1.20.0 to 1.21.0 (#1808)
Update stevedore from 1.20.0 to 1.21.0 (#1808)


alex/warehouse,alex/warehouse,pypa/warehouse,dstufft/warehouse,alex/warehouse,dstufft/warehouse,pypa/warehouse,dstufft/warehouse,alex/warehouse,pypa/warehouse,alex/warehouse,pypa/warehouse,dstufft/warehouse