message: test_node: get_mem_rss fixups
diff: @@ -118,22 +118,19 @@ class TestNode():
  def get_mem_rss(self):
  """Get the memory usage (RSS) per `ps`.
  - If process is stopped or `ps` is unavailable, return None.
  + Returns None if `ps` is unavailable.
  """
  - if not (self.running and self.process):
  - self.log.warning("Couldn't get memory usage; process isn't running.")
  - return None
  + assert self.running
  try:
  return int(subprocess.check_output(
  - "ps h -o rss {}".format(self.process.pid),
  - shell=True, stderr=subprocess.DEVNULL).strip())
  + ["ps", "h", "-o", "rss", "{}".format(self.process.pid)],
  + stderr=subprocess.DEVNULL).split()[-1])
  - # Catching `Exception` broadly to avoid failing on platforms where ps
  - # isn't installed or doesn't work as expected, e.g. OpenBSD.
  + # Avoid failing on platforms where ps isn't installed.
  #
  # We could later use something like `psutils` to work across platforms.
  - except Exception:
  + except (FileNotFoundError, subprocess.SubprocessError):
  self.log.exception("Unable to get memory usage")
  return None
  @@ -308,7 +305,7 @@ class TestNode():
  self.log.warning("Unable to detect memory usage (RSS) - skipping memory check.")
  return
  - perc_increase_memory_usage = 1 - (float(before_memory_usage) / after_memory_usage)
  + perc_increase_memory_usage = (after_memory_usage / before_memory_usage) - 1
  if perc_increase_memory_usage > perc_increase_allowed:
  self._raise_assertion_error(
  