Pull controller-go back into this repository as internal/controllerlib.

Signed-off-by: Matt Moyer <moyerm@vmware.com>

internal/controllerlib/error.go

@@ -0,0 +1,18 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package controllerlib
+
+// ErrSyntheticRequeue can be returned from a Syncer to force a retry artificially for the current key.
+// This can also be done by re-adding the key to queue, but this is more convenient and has better logging.
+const ErrSyntheticRequeue = constErr("synthetic requeue request")
+
+var _ error = constErr("")
+
+type constErr string
+
+func (e constErr) Error() string {
+	return string(e)
+}