Fix a unit test (#844)
Fix a unit test (#844)

Before asserting that something doesn't exist, assert that it used to exist.

We were checking that a package object is not in a list of strings... Of course it's not - it's not a string.
quiltdata/quilt,quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt