Make Python code more idiomatic

whipper/program/cdparanoia.py

@@ -238,7 +238,7 @@ class ReadTrackTask(task.Task):
         @param what:   a string representing what's being read; e.g. Track
         @type  what:   str
         """
-        assert type(path) is unicode, "%r is not unicode" % path
+        assert isinstance(path, unicode), "%r is not unicode" % path
 
         self.path = path
         self._table = table

whipper/program/soxi.py

@@ -23,7 +23,7 @@ class AudioLengthTask(ctask.PopenTask):
         """
         @type  path: unicode
         """
-        assert type(path) is unicode, "%r is not unicode" % path
+        assert isinstance(path, unicode), "%r is not unicode" % path
 
         self.logName = os.path.basename(path).encode('utf-8')