code: def get_sha(a_file, settings=None):
      
      if settings:
          error = settings["error"]
      else:
          error = ERROR_FN
      try:
          BLOCKSIZE = 65536
          hasher = hashlib.sha1()
          with io.open(a_file, "rb") as fh:
              buf = fh.read(BLOCKSIZE)
              while len(buf) > 0:
                  hasher.update(buf)
                  buf = fh.read(BLOCKSIZE)
          the_hash = hasher.hexdigest()
      except IOError:
          errmes = "File '{}' could not be read! Exiting!".format(a_file)
          error(errmes)
          sys.exit(1)
      except:
          errmes = "Unspecified error returning sha1 hash. Exiting!"
          error(errmes)
          sys.exit(1)
      return the_hash
docs: Returns sha1 hash of the file supplied as an argument