message: tests: Add a sha256sum_file function to util
diff: @@ -8,6 +8,7 @@ from base64 import b64encode
  from binascii import unhexlify
  from decimal import Decimal, ROUND_DOWN
  from subprocess import CalledProcessError
  +import hashlib
  import inspect
  import json
  import logging
  @@ -260,6 +261,14 @@ def wait_until_helper(predicate, *, attempts=float('inf'), timeout=float('inf'),
  raise AssertionError("Predicate {} not true after {} seconds".format(predicate_source, timeout))
  raise RuntimeError('Unreachable')
  +def sha256sum_file(filename):
  + h = hashlib.sha256()
  + with open(filename, 'rb') as f:
  + d = f.read(4096)
  + while len(d) > 0:
  + h.update(d)
  + d = f.read(4096)
  + return h.digest()
  # RPC/P2P connection constants and functions
  ############################################
  