code: def find_standard_sakefile(settings):
      
      error = settings["error"]
      if settings["customsake"]:
          custom = settings["customsake"]
          if not os.path.isfile(custom):
              error("Specified sakefile '{}' doesn't exist", custom)
              sys.exit(1)
          return custom
      # no custom specified, going over defaults in order
      for name in ["Sakefile", "Sakefile.yaml", "Sakefile.yml"]:
          if os.path.isfile(name):
              return name
      error("Error: there is no Sakefile to read")
      sys.exit(1)
docs: Returns the filename of the appropriate sakefile