Improve checkState logging if getKey() is called on an unexported StarlarkProvider.

PiperOrigin-RevId: 683139443
Change-Id: Ia58f22be486325a48233da7053a9cdc8cbc3289b

src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java

diff --git a/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java b/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
index 03ae3b5..db49ec2 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
@@ -345,7 +345,12 @@
 
   @Override
   public Key getKey() {
-    Preconditions.checkState(isExported());
+    Preconditions.checkState(
+        isExported(),
+        "Calling getKey() is disallowed on an unexported provider. location: %s, identity token:"
+            + " %s",
+        location,
+        keyOrIdentityToken);
     return (Key) keyOrIdentityToken;
   }