Add call_maybe(): a variant of call_method() that returns NotImplemented when the lookup fails, and use this for binary operators.  Also lookup_maybe() which doesn't raise an exception when the lookup fails (still returning NULL).
Add call_maybe(): a variant of call_method() that returns
NotImplemented when the lookup fails, and use this for binary
operators.  Also lookup_maybe() which doesn't raise an exception when
the lookup fails (still returning NULL).

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator