Remove github.com/pkg/errors and replace with std library version

This is possible now that we no longer support go1.12 and brings
rclone into line with standard practices in the Go world.

This also removes errors.New and errors.Errorf from lib/errors and
prefers the stdlib errors package over lib/errors.

backend/box/upload.go

@@ -8,6 +8,7 @@ import (
 	"crypto/sha1"
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -15,7 +16,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/pkg/errors"
 	"github.com/rclone/rclone/backend/box/api"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/accounting"
@@ -140,7 +140,7 @@ outer:
 					}
 				}
 			default:
-				return nil, errors.Errorf("unknown HTTP status return %q (%d)", resp.Status, resp.StatusCode)
+				return nil, fmt.Errorf("unknown HTTP status return %q (%d)", resp.Status, resp.StatusCode)
 			}
 		}
 		fs.Debugf(o, "commit multipart upload failed %d/%d - trying again in %d seconds (%s)", tries+1, maxTries, delay, why)
@@ -151,7 +151,7 @@ outer:
 	}
 	err = json.Unmarshal(body, &result)
 	if err != nil {
-		return nil, errors.Wrapf(err, "couldn't decode commit response: %q", body)
+		return nil, fmt.Errorf("couldn't decode commit response: %q: %w", body, err)
 	}
 	return result, nil
 }
@@ -177,7 +177,7 @@ func (o *Object) uploadMultipart(ctx context.Context, in io.Reader, leaf, direct
 	// Create upload session
 	session, err := o.createUploadSession(ctx, leaf, directoryID, size)
 	if err != nil {
-		return errors.Wrap(err, "multipart upload create session failed")
+		return fmt.Errorf("multipart upload create session failed: %w", err)
 	}
 	chunkSize := session.PartSize
 	fs.Debugf(o, "Multipart upload session started for %d parts of size %v", session.TotalParts, fs.SizeSuffix(chunkSize))
@@ -222,7 +222,7 @@ outer:
 		// Read the chunk
 		_, err = io.ReadFull(in, buf)
 		if err != nil {
-			err = errors.Wrap(err, "multipart upload failed to read source")
+			err = fmt.Errorf("multipart upload failed to read source: %w", err)
 			break outer
 		}
 
@@ -238,7 +238,7 @@ outer:
 			fs.Debugf(o, "Uploading part %d/%d offset %v/%v part size %v", part+1, session.TotalParts, fs.SizeSuffix(position), fs.SizeSuffix(size), fs.SizeSuffix(chunkSize))
 			partResponse, err := o.uploadPart(ctx, session.ID, position, size, buf, wrap, options...)
 			if err != nil {
-				err = errors.Wrap(err, "multipart upload failed to upload part")
+				err = fmt.Errorf("multipart upload failed to upload part: %w", err)
 				select {
 				case errs <- err:
 				default:
@@ -266,11 +266,11 @@ outer:
 	// Finalise the upload session
 	result, err := o.commitUpload(ctx, session.ID, parts, modTime, hash.Sum(nil))
 	if err != nil {
-		return errors.Wrap(err, "multipart upload failed to finalize")
+		return fmt.Errorf("multipart upload failed to finalize: %w", err)
 	}
 
 	if result.TotalCount != 1 || len(result.Entries) != 1 {
-		return errors.Errorf("multipart upload failed %v - not sure why", o)
+		return fmt.Errorf("multipart upload failed %v - not sure why", o)
 	}
 	return o.setMetaData(&result.Entries[0])
 }