Replace deprecated inspect.getargspec

inspect.getargspec was deprecated since Python 3.0 and
inspect.getfullargspec is its replacement with correct handling of
function annotations and keyword-only parameters[1].

[1] https://docs.python.org/3/library/inspect.html#inspect.getargspec

Change-Id: I29478df88665ee5311e3ba308ab645c47e5b0fc8