AssertNamespacePrefix cannot add new namespaces in virtual datasets

[rompetroll]

datahub/dataset_http_integration_test.go

Line 165 in 226f3b0

js := `function build_entities(params = {}, since = "", limit = -1) {

See the test script above, if AssertNamespacePrefix would create previously unknown prefixes, then the prefixes would be stored correctly in datahub. But the http response would already have the context comiitted. So newly created prefixes would be missing in the output.

On subsequent requests to the same virtual dataset, the prefixes would not be new anymore - and therefore be in the context. So this is only an issue with first requests to a virtual dataset