Improve error messages, esp. when the server is running

* Add file context to minifier errors when publishing
* Misc fixes (see issues)
* Allow custom server error template in layouts/server/error.html

To get to this, this commit also cleans up and simplifies the code surrounding errors and files. This also removes the usage of `github.com/pkg/errors`, mostly because of https://github.com/pkg/errors/issues/223 -- but also because most of this is now built-in to Go.

Fixes #9852
Fixes #9857
Fixes #9863

hugofs/decorators.go

@@ -14,12 +14,11 @@
 package hugofs
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
 
-	"github.com/pkg/errors"
-
 	"github.com/spf13/afero"
 )
 
@@ -232,7 +231,7 @@ func (l *baseFileDecoratorFile) Readdir(c int) (ofi []os.FileInfo, err error) {
 		}
 		fi, err = l.fs.decorate(fi, filename)
 		if err != nil {
-			return nil, errors.Wrap(err, "decorate")
+			return nil, fmt.Errorf("decorate: %w", err)
 		}
 		fisp = append(fisp, fi)
 	}

hugofs/fileinfo.go

@@ -28,7 +28,7 @@ import (
 	"github.com/gohugoio/hugo/hugofs/files"
 	"golang.org/x/text/unicode/norm"
 
-	"github.com/pkg/errors"
+	"errors"
 
 	"github.com/gohugoio/hugo/common/hreflect"
 

hugofs/rootmapping_fs.go

@@ -21,8 +21,6 @@ import (
 
 	"github.com/gohugoio/hugo/hugofs/files"
 
-	"github.com/pkg/errors"
-
 	radix "github.com/armon/go-radix"
 	"github.com/spf13/afero"
 )
@@ -191,7 +189,7 @@ func (fs *RootMappingFs) Dirs(base string) ([]FileMetaInfo, error) {
 		fs = decorateDirs(fs, r.Meta)
 		fi, err := fs.Stat("")
 		if err != nil {
-			return nil, errors.Wrap(err, "RootMappingFs.Dirs")
+			return nil, fmt.Errorf("RootMappingFs.Dirs: %w", err)
 		}
 
 		if !fi.IsDir() {
@@ -560,7 +558,7 @@ func (fs *RootMappingFs) doLstat(name string) ([]FileMetaInfo, error) {
 
 	if fileCount > 1 {
 		// Not supported by this filesystem.
-		return nil, errors.Errorf("found multiple files with name %q, use .Readdir or the source filesystem directly", name)
+		return nil, fmt.Errorf("found multiple files with name %q, use .Readdir or the source filesystem directly", name)
 	}
 
 	return []FileMetaInfo{roots[0].fi}, nil

hugofs/slice_fs.go

@@ -14,11 +14,12 @@
 package hugofs
 
 import (
+	"fmt"
 	"os"
 	"syscall"
 	"time"
 
-	"github.com/pkg/errors"
+	"errors"
 
 	"github.com/spf13/afero"
 )
@@ -83,7 +84,7 @@ func (fs *SliceFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {
 		return decorateFileInfo(fi, fs, fs.getOpener(name), "", "", nil), false, nil
 	}
 
-	return nil, false, errors.Errorf("lstat: files not supported: %q", name)
+	return nil, false, fmt.Errorf("lstat: files not supported: %q", name)
 }
 
 func (fs *SliceFs) Mkdir(n string, p os.FileMode) error {

hugofs/walk.go

@@ -22,7 +22,7 @@ import (
 
 	"github.com/gohugoio/hugo/common/loggers"
 
-	"github.com/pkg/errors"
+	"errors"
 
 	"github.com/spf13/afero"
 )
@@ -125,7 +125,7 @@ func (w *Walkway) Walk() error {
 			if w.checkErr(w.root, err) {
 				return nil
 			}
-			return w.walkFn(w.root, nil, errors.Wrapf(err, "walk: %q", w.root))
+			return w.walkFn(w.root, nil, fmt.Errorf("walk: %q: %w", w.root, err))
 		}
 		fi = info.(FileMetaInfo)
 	}
@@ -192,7 +192,7 @@ func (w *Walkway) walk(path string, info FileMetaInfo, dirEntries []FileMetaInfo
 			if w.checkErr(path, err) {
 				return nil
 			}
-			return walkFn(path, info, errors.Wrapf(err, "walk: open %q (%q)", path, w.root))
+			return walkFn(path, info, fmt.Errorf("walk: open %q (%q): %w", path, w.root, err))
 		}
 
 		fis, err := f.Readdir(-1)
@@ -201,7 +201,7 @@ func (w *Walkway) walk(path string, info FileMetaInfo, dirEntries []FileMetaInfo
 			if w.checkErr(filename, err) {
 				return nil
 			}
-			return walkFn(path, info, errors.Wrap(err, "walk: Readdir"))
+			return walkFn(path, info, fmt.Errorf("walk: Readdir: %w", err))
 		}
 
 		dirEntries = fileInfosToFileMetaInfos(fis)

hugofs/walk_test.go

@@ -22,7 +22,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/pkg/errors"
+	"errors"
 
 	"github.com/gohugoio/hugo/common/para"
 	"github.com/gohugoio/hugo/htesting"