remove copied code from testfile

Because the test file driver only had ListerForURI() so it would satisfy
the driver interface, but this code was not actually used, it has been
removed and replaced with a stub that returns an error message, similar
to the mobile driver.

test/testfile.go

@@ -3,7 +3,6 @@ package test
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -57,51 +56,6 @@ func (d *testDriver) FileWriterForURI(uri fyne.URI) (fyne.URIWriteCloser, error)
 	return openFile(uri, true)
 }
 
-// lazily copied over from the glfw driver, should be good enough for testing
-// purposes
-
-type directory struct {
-	fyne.URI
-}
-
-// Declare conformity to the ListableURI interface
-var _ fyne.ListableURI = (*directory)(nil)
-
-func (d *directory) List() ([]fyne.URI, error) {
-	if d.Scheme() != "file" {
-		return nil, fmt.Errorf("unsupported URL protocol")
-	}
-
-	path := d.String()[len(d.Scheme())+3 : len(d.String())]
-	files, err := ioutil.ReadDir(path)
-	if err != nil {
-		return nil, err
-	}
-
-	urilist := []fyne.URI{}
-
-	for _, f := range files {
-		uri := storage.NewURI("file://" + filepath.Join(path, f.Name()))
-		urilist = append(urilist, uri)
-	}
-
-	return urilist, nil
-}
-
 func (d *testDriver) ListerForURI(uri fyne.URI) (fyne.ListableURI, error) {
-	if uri.Scheme() != "file" {
-		return nil, fmt.Errorf("unsupported URL protocol")
-	}
-
-	path := uri.String()[len(uri.Scheme())+3 : len(uri.String())]
-	s, err := os.Stat(path)
-	if err != nil {
-		return nil, err
-	}
-
-	if !s.IsDir() {
-		return nil, fmt.Errorf("Path '%s' is not a directory, cannot convert to listable URI", path)
-	}
-
-	return &directory{URI: uri}, nil
+	return nil, fmt.Errorf("test driver does support creating listable URIs yet")
 }