bzlmod: Proper error reporting with ExternalDepsException

(https://github.com/bazelbuild/bazel/issues/13316)

PiperOrigin-RevId: 385980424
diff --git a/src/main/java/com/google/devtools/build/lib/util/ExitCode.java b/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
index c821a24..f91fffa 100644
--- a/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
+++ b/src/main/java/com/google/devtools/build/lib/util/ExitCode.java
@@ -67,6 +67,7 @@
       ExitCode.createInfrastructureFailure(38, "PUBLISH_ERROR");
   public static final ExitCode PERSISTENT_BUILD_EVENT_SERVICE_UPLOAD_ERROR =
       ExitCode.create(45, "PERSISTENT_BUILD_EVENT_SERVICE_UPLOAD_ERROR");
+  public static final ExitCode EXTERNAL_DEPS_ERROR = ExitCode.create(48, "EXTERNAL_DEPS_ERROR");
 
   /**
    * Creates and returns an ExitCode.  Requires a unique exit code number.