code: def listFiles(self):
          
          def fn(dirName, level, files):
              if level == self.levelNo-1:
                  for fileName in os.listdir(dirName):
                      if fileName != "lock":
                          absFileName = os.path.join(dirName, fileName)
                          files.append(absFileName)
              else:
                  for subDir in os.listdir(dirName):
                      if subDir != "lock":
                          absDirName = os.path.join(dirName, subDir)
                          assert os.path.isdir(absDirName)
                          fn(absDirName, level+1, files)
          files = []
          fn(self.rootDir, 0, files)
          return files
docs: Gets all files in the temp file tree (which may be dirs).