diff -U3 /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/../pgsql/src/test/regress/expected/vacuum.out /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/src/test/regress/results/vacuum.out
--- /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/../pgsql/src/test/regress/expected/vacuum.out	2019-08-11 03:02:18.921535948 -0700
+++ /home/pgsql/build-farm/buildroot-clang/HEAD/pgsql.build/src/test/regress/results/vacuum.out	2019-11-05 00:50:42.381244885 -0800
@@ -204,6 +204,7 @@
 -- SKIP_LOCKED option
 VACUUM (SKIP_LOCKED) vactst;
 VACUUM (SKIP_LOCKED, FULL) vactst;
+WARNING:  skipping vacuum of "vactst" --- lock not available
 ANALYZE (SKIP_LOCKED) vactst;
 -- ensure VACUUM and ANALYZE don't have a problem with serializable
 SET default_transaction_isolation = serializable;