Convert panics to errors for public interface

org/html_test.go

@@ -8,9 +8,12 @@ import (
 func TestHTMLWriter(t *testing.T) {
 	for _, path := range orgTestFiles() {
 		reader, writer := strings.NewReader(fileString(path)), NewHTMLWriter()
-		actual := NewDocument().Parse(reader).Write(writer).String()
+		actual, err := NewDocument().Parse(reader).Write(writer)
+		if err != nil {
+			t.Errorf("%s\n got error: %s", path, err)
+			continue
+		}
 		expected := fileString(path[:len(path)-len(".org")] + ".html")
-
 		if expected != actual {
 			t.Errorf("%s:\n%s'", path, diff(actual, expected))
 		} else {