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/http/http.go

@@ -6,6 +6,8 @@ package http
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"io"
 	"mime"
 	"net/http"
@@ -16,7 +18,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/pkg/errors"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/config/configmap"
 	"github.com/rclone/rclone/fs/config/configstruct"
@@ -132,7 +133,7 @@ func statusError(res *http.Response, err error) error {
 	}
 	if res.StatusCode < 200 || res.StatusCode > 299 {
 		_ = res.Body.Close()
-		return errors.Errorf("HTTP Error %d: %s", res.StatusCode, res.Status)
+		return fmt.Errorf("HTTP Error %d: %s", res.StatusCode, res.Status)
 	}
 	return nil
 }
@@ -377,15 +378,15 @@ func (f *Fs) readDir(ctx context.Context, dir string) (names []string, err error
 	URL := f.url(dir)
 	u, err := url.Parse(URL)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to readDir")
+		return nil, fmt.Errorf("failed to readDir: %w", err)
 	}
 	if !strings.HasSuffix(URL, "/") {
-		return nil, errors.Errorf("internal error: readDir URL %q didn't end in /", URL)
+		return nil, fmt.Errorf("internal error: readDir URL %q didn't end in /", URL)
 	}
 	// Do the request
 	req, err := http.NewRequestWithContext(ctx, "GET", URL, nil)
 	if err != nil {
-		return nil, errors.Wrap(err, "readDir failed")
+		return nil, fmt.Errorf("readDir failed: %w", err)
 	}
 	f.addHeaders(req)
 	res, err := f.httpClient.Do(req)
@@ -397,7 +398,7 @@ func (f *Fs) readDir(ctx context.Context, dir string) (names []string, err error
 	}
 	err = statusError(res, err)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to readDir")
+		return nil, fmt.Errorf("failed to readDir: %w", err)
 	}
 
 	contentType := strings.SplitN(res.Header.Get("Content-Type"), ";", 2)[0]
@@ -405,10 +406,10 @@ func (f *Fs) readDir(ctx context.Context, dir string) (names []string, err error
 	case "text/html":
 		names, err = parse(u, res.Body)
 		if err != nil {
-			return nil, errors.Wrap(err, "readDir")
+			return nil, fmt.Errorf("readDir: %w", err)
 		}
 	default:
-		return nil, errors.Errorf("Can't parse content type %q", contentType)
+		return nil, fmt.Errorf("Can't parse content type %q", contentType)
 	}
 	return names, nil
 }
@@ -428,7 +429,7 @@ func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err e
 	}
 	names, err := f.readDir(ctx, dir)
 	if err != nil {
-		return nil, errors.Wrapf(err, "error listing %q", dir)
+		return nil, fmt.Errorf("error listing %q: %w", dir, err)
 	}
 	var (
 		entriesMu sync.Mutex // to protect entries
@@ -540,7 +541,7 @@ func (o *Object) stat(ctx context.Context) error {
 	url := o.url()
 	req, err := http.NewRequestWithContext(ctx, "HEAD", url, nil)
 	if err != nil {
-		return errors.Wrap(err, "stat failed")
+		return fmt.Errorf("stat failed: %w", err)
 	}
 	o.fs.addHeaders(req)
 	res, err := o.fs.httpClient.Do(req)
@@ -549,7 +550,7 @@ func (o *Object) stat(ctx context.Context) error {
 	}
 	err = statusError(res, err)
 	if err != nil {
-		return errors.Wrap(err, "failed to stat")
+		return fmt.Errorf("failed to stat: %w", err)
 	}
 	t, err := http.ParseTime(res.Header.Get("Last-Modified"))
 	if err != nil {
@@ -562,7 +563,7 @@ func (o *Object) stat(ctx context.Context) error {
 	if o.fs.opt.NoSlash {
 		mediaType, _, err := mime.ParseMediaType(o.contentType)
 		if err != nil {
-			return errors.Wrapf(err, "failed to parse Content-Type: %q", o.contentType)
+			return fmt.Errorf("failed to parse Content-Type: %q: %w", o.contentType, err)
 		}
 		if mediaType == "text/html" {
 			return fs.ErrorNotAFile
@@ -588,7 +589,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.Read
 	url := o.url()
 	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
 	if err != nil {
-		return nil, errors.Wrap(err, "Open failed")
+		return nil, fmt.Errorf("Open failed: %w", err)
 	}
 
 	// Add optional headers
@@ -601,7 +602,7 @@ func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.Read
 	res, err := o.fs.httpClient.Do(req)
 	err = statusError(res, err)
 	if err != nil {
-		return nil, errors.Wrap(err, "Open failed")
+		return nil, fmt.Errorf("Open failed: %w", err)
 	}
 	return res.Body, nil
 }