Fix Logger interface.

logging/file.go

@@ -20,6 +20,8 @@ func (fl *File) Close() error {
 	if fl.fe != nil {
 		return fl.fe.Close()
 	}
+
+	return nil
 }
 
 // NewFile creates a new Logger that writes all logs to the file

logging/log.go

@@ -21,7 +21,7 @@ type Logger interface {
 	Status() error
 
 	// Close gives the Logger the opportunity to perform any cleanup.
-	Close()
+	Close() error
 
 	// Log messages consist of four components:
 	//
@@ -276,4 +276,4 @@ func (lw *LogWriter) SetLevel(l Level) {
 }
 
 // Close is a no-op that satisfies the Logger interface.
-func (lw *LogWriter) Close() {}
+func (lw *LogWriter) Close() error { return nil }