code: def find_exe(name, filepath=None):
      
      if filepath:
          if not os.path.exists(filepath):
              open(filepath)  # raise IOError
          elif not os.path.isfile(filepath):
              raise RezBindError("not a file: %s" % filepath)
      else:
          filepath = which(name)
          if not filepath:
              raise RezBindError("could not find executable: %s" % name)
  
      return filepath
docs: Find an executable.
  
      Args:
          name: Name of the program, eg 'python'.
          filepath: Path to executable, a search is performed if None.
  
      Returns:
          Path to the executable if found, otherwise an error is raised.