bundlespec: fix the "streamv2" and "streamv3-exp" variant
In c4aab3661f25, we broken this feature by adding unicode instead of bytes to
the dictionary.
On the other hand, this feature was never tested, so augment the tests to tests
this.
# Tests to be disabled when building and testing in the Nix sandbox.
# tests enforcing "/usr/bin/env" shebangs, which are patched for nix
test-run-tests.t
test-check-shbang.t
# doesn't like the extra setlocale warnings emitted by the nix bash wrappers
test-locale.t