Tweaks to callgraph.py so it can walk byterun.

Hooking up byterun to opy_main.py caused some errors.

(byterun will probably never be shipped, at least not in its current
form.  But it's still useful to see what code is used transitively.)

opy/callgraph.py

@@ -141,15 +141,22 @@ def _Walk(obj, cls, ref, syms):
  #  log('OBJ %s %d', obj, id(obj))
  #  pass
   
  if module_name is None:
  # Oh is the namedtuple_ crap because of the Block class byterun/pyobj?
  
  if module_name is None or module_name in (
      'namedtuple_Arguments', 'namedtuple_ArgSpec',
      'namedtuple_Block'):
    syms.Add(obj, None, ref, None, None, None)
    return  # Can't walk anything

  #log('OBJ %s %d', obj, id(obj))
  module = sys.modules[obj.__module__]

  #print(obj)
  if hasattr(obj, '__code__'):  # Builtins don't have bytecode.
  co = getattr(obj, '__code__', None)
  # For example, Builtins don't have bytecode.
  if isinstance(co, types.CodeType):
    co = obj.__code__
    #log('CO %s', co)
    #path = co.co_filename

    mod_name = None
@@ -348,7 +355,10 @@ def Add(self, obj, cls, ref, mod_name, mod_path, line_num):
      # NOTE: Python's classes don't have a __code__ object, which appears to
      # be an irregularity.  So we have to get location information from the
      # METHODS.
      assert not hasattr(obj, '__code__'), obj

      # Exception: this type has a __code__ object that is not types.CodeType
      if obj is not types.FunctionType:
        assert not hasattr(obj, '__code__'), obj
      #assert path is None
      assert line_num is None