cleanup: move pkg/ to internal/

The internal/ directory in Go has a special meaning, and indicates that
those packages are not meant for external consumption. Ceph-CSI does
provide public APIs for other projects to consume. There is no plan to
keep the API of the internally used packages stable.

Closes: #903
Signed-off-by: Niels de Vos <ndevos@redhat.com>

internal/util/errors.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2019 The Ceph-CSI Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+// ErrKeyNotFound is returned when requested key in omap is not found
+type ErrKeyNotFound struct {
+	keyName string
+	err     error
+}
+
+func (e ErrKeyNotFound) Error() string {
+	return e.err.Error()
+}
+
+// ErrObjectExists is returned when named omap is already present in rados
+type ErrObjectExists struct {
+	objectName string
+	err        error
+}
+
+func (e ErrObjectExists) Error() string {
+	return e.err.Error()
+}
+
+// ErrObjectNotFound is returned when named omap is not found in rados
+type ErrObjectNotFound struct {
+	oMapName string
+	err      error
+}
+
+func (e ErrObjectNotFound) Error() string {
+	return e.err.Error()
+}
+
+// ErrSnapNameConflict is generated when a requested CSI snap name already exists on RBD but with
+// different properties, and hence is in conflict with the passed in CSI volume name
+type ErrSnapNameConflict struct {
+	requestName string
+	err         error
+}
+
+func (e ErrSnapNameConflict) Error() string {
+	return e.err.Error()
+}
+
+// ErrPoolNotFound is returned when pool is not found
+type ErrPoolNotFound struct {
+	Pool string
+	Err  error
+}
+
+func (e ErrPoolNotFound) Error() string {
+	return e.Err.Error()
+}