More informative -MISCONF error message.

src/server.c

@@ -1272,7 +1272,7 @@ void createSharedObjects(void) {
     shared.masterdownerr = createObject(OBJ_STRING,sdsnew(
         "-MASTERDOWN Link with MASTER is down and slave-serve-stale-data is set to 'no'.\r\n"));
     shared.bgsaveerr = createObject(OBJ_STRING,sdsnew(
-        "-MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.\r\n"));
+        "-MISCONF Redis is configured to save RDB snapshots, but it is currently not able to persist on disk. Commands that may modify the data set are disabled, because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option). Please check the Redis logs for details about the RDB error.\r\n"));
     shared.roslaveerr = createObject(OBJ_STRING,sdsnew(
         "-READONLY You can't write against a read only slave.\r\n"));
     shared.noautherr = createObject(OBJ_STRING,sdsnew(