old_contents: ﻿def build(source_path, overwrite = True):
      pass
new_contents: ﻿import os.path
  def build(source_path, overwrite = True):
      if not os.path.exists(source_path):
          raise IOError("source_path does not exist so not skeleton can be built")
      '''
      for root, dirs, files in os.walk("."):
      path = root.split('/')
      print (len(path) - 1) *'---' , os.path.basename(root)       
      for file in files:
          print len(path)*'---', file
      '''
subject: Make the first test pass by checking if source_path argument exists