[Python-Dev] Enum, Flag, __contains__, and False vs TypeError

[Serhiy Storchaka]

I expect that for IntFlag `x in flags` is equivalent either to

     bool(x | flags.value)

or to

     (x | flags.value) == x

It should return some result only if x is an integer (or compatible with 
integers) and raise a TypeError otherwise.

Don't add any special checks unless there are good reasons for this. 
Keep the code as simple as possible.