Fix monitor thread crash when a phase carries extra_kwargs

[rootkiller6788]

Problem

openhtf/core/monitors.py _MonitorThread.get_value() filtered the monitored phase's extra_kwargs with:

kwargs = {arg: val for arg, val in self.extra_kwargs if arg in argspec_args}

self.extra_kwargs is a dict (see PhaseDescriptor.extra_kwargs), so iterating it yields its keys. Each key (a string) is then unpacked into arg, val, which raises:

ValueError: too many values to unpack (expected 2)

This happens whenever a phase is parameterized with PhaseDescriptor.with_args(...) (so it carries extra_kwargs) and the monitor function does not take **kwargs. The monitor thread crashes and the test run fails.

Reproduction

import openhtf
from openhtf.core import monitors
from openhtf.core import phase_descriptor

def monitor_func(test):
  return 1

def phase(test, port):
  pass

phase_desc = phase_descriptor.PhaseDescriptor(phase).with_args(port=1234)
monitored = monitors.monitors('meas', monitor_func)(phase_desc)

test = openhtf.Test(monitored)
test.execute(test_start=lambda: 'MyDutId')

Before the fix this logs ValueError: too many values to unpack (expected 2) in meas_MonitorThread and the test FAILs.

Fix

Iterate over self.extra_kwargs.items() instead of the dict itself.

Tests

Added test_get_value_with_extra_kwargs in test/core/monitors_test.py, which exercises a monitor without **kwargs against a phase descriptor carrying extra_kwargs. It fails on master and passes with the fix.