Make the error message for missing outputs more useful

Don't only show the name of the output, but also the derivation to which
this output belongs (as otherwise it's very hard to track back what went
wrong)

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 01e2fcc7b..9da415c42 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -394,7 +394,7 @@ OutputPathMap Store::queryDerivationOutputMap(const StorePath & path) {
     OutputPathMap result;
     for (auto & [outName, optOutPath] : resp) {
         if (!optOutPath)
-            throw Error("output '%s' has no store path mapped to it", outName);
+            throw Error("output '%s' of derivation '%s' has no store path mapped to it", outName, printStorePath(path));
         result.insert_or_assign(outName, *optOutPath);
     }
     return result;