Fix why-depends for CA derivations (again)

This has the same goal as b13fd4c58e81b2b2b0d72caa5ce80de861622610,but
achieves it in a different way in order to not break
`nix why-depends --derivation`.

1 files changed, 1 insertions, 4 deletions

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index d2600ca91..b5675d5bd 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -931,10 +931,7 @@ std::vector<std::pair<std::shared_ptr<Installable>, BuiltPathWithResult>> Instal
                                 DrvOutput outputId { *outputHash, output };
                                 auto realisation = store->queryRealisation(outputId);
                                 if (!realisation)
-                                    throw Error(
-                                        "cannot operate on an output of the "
-                                        "unbuilt derivation '%s'",
-                                        outputId.to_string());
+                                    throw MissingRealisation(outputId);
                                 outputs.insert_or_assign(output, realisation->outPath);
                             } else {
                                 // If ca-derivations isn't enabled, assume that