python: Replace 'getargspec' with 'signature' in SimObject.py

In Python 3.11 'inspect.getargspec' has been removed. It has been
marked for deprecation since 3.5. The SimObject.py class has therefore
been rewritten to use 'inspect.signature' instead.

Change-Id: I9efd831e05e0b1619f366ffe722abb0a072fd519
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/68817
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/m5/SimObject.py

@@ -478,19 +478,21 @@ def cxxMethod(*args, **kwargs):
         return_value_policy = kwargs.get("return_value_policy", None)
         static = kwargs.get("static", False)
 
-        args, varargs, keywords, defaults = inspect.getargspec(func)
-        if varargs or keywords:
-            raise ValueError(
-                "Wrapped methods must not contain variable arguments"
-            )
-
-        # Create tuples of (argument, default)
-        if defaults:
-            args = args[: -len(defaults)] + list(
-                zip(args[-len(defaults) :], defaults)
-            )
-        # Don't include self in the argument list to PyBind
-        args = args[1:]
+        # Create a list of tuples of (argument, default). The `PyBindMethod`
+        # class expects the `args` argument to be a list of either argument
+        # names, in the case that argument does not have a default value, and
+        # a tuple of (argument, default) in the casae where an argument does.
+        args = []
+        sig = inspect.signature(func)
+        for param_name in sig.parameters.keys():
+            if param_name == "self":
+                # We don't cound 'self' as an argument in this case.
+                continue
+            param = sig.parameters[param_name]
+            if param.default is param.empty:
+                args.append(param_name)
+            else:
+                args.append((param_name, param.default))
 
         @wraps(func)
         def cxx_call(self, *args, **kwargs):