cleanup: move cephfs errors to new util package

As part of the refactoring, moving the cephfs errors file to a new
package.

Updates: #852
Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/cephfs/errors/errors.go

@@ -0,0 +1,64 @@
+/*
+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 errors
+
+import (
+	coreError "errors"
+)
+
+// Error strings for comparison with CLI errors.
+const (
+	// VolumeNotEmpty is returned when the volume is not empty.
+	VolumeNotEmpty = "Directory not empty"
+)
+
+var (
+	// ErrCloneInProgress is returned when snapshot clone state is `in progress`.
+	ErrCloneInProgress = coreError.New("clone from snapshot is already in progress")
+
+	// ErrClonePending is returned when snapshot clone state is `pending`.
+	ErrClonePending = coreError.New("clone from snapshot is pending")
+
+	// ErrInvalidClone is returned when the clone state is invalid.
+	ErrInvalidClone = coreError.New("invalid clone state")
+
+	// ErrCloneFailed is returned when the clone state is failed.
+	ErrCloneFailed = coreError.New("clone from snapshot failed")
+
+	// ErrInvalidVolID is returned when a CSI passed VolumeID is not conformant to any known volume ID
+	// formats.
+	ErrInvalidVolID = coreError.New("invalid VolumeID")
+	// ErrNonStaticVolume is returned when a volume is detected as not being
+	// statically provisioned.
+	ErrNonStaticVolume = coreError.New("volume not static")
+
+	// ErrSnapProtectionExist is returned when the snapshot is already protected.
+	ErrSnapProtectionExist = coreError.New("snapshot  protection already exists")
+
+	// ErrSnapNotFound is returned when snap name passed is not found in the list
+	// of snapshots for the given image.
+	ErrSnapNotFound = coreError.New("snapshot not found")
+
+	// ErrVolumeNotFound is returned when a subvolume is not found in CephFS.
+	ErrVolumeNotFound = coreError.New("volume not found")
+
+	// ErrInvalidCommand is returned when a command is not known to the cluster.
+	ErrInvalidCommand = coreError.New("invalid command")
+
+	// ErrVolumeHasSnapshots is returned when a subvolume has snapshots.
+	ErrVolumeHasSnapshots = coreError.New("volume has snapshots")
+)