Remove python future compatibility library and remove more python 2 compatibility code.

[jameshilliard]

No description provided.

[kristapsk]

Some tests are failing for me with this, unless #538 is applied on top, so I think that should be merged before more reviewing testing is done here (platform linux -- Python 3.6.5, pytest-5.4.1, py-1.8.1, pluggy-0.13.1 with failing tests).

[AdamISZ]

Just double checked - indeed there are test failures with Python 3.6.8, pytest-5.4.1, py-1.8.1, pluggy-0.13.1 - but that's exactly as expected, no PRs will pass with 5.4.1 as I was mentioning I think on IRC. #538 is going to be needed for any test to pass from now on - and even that won't be enough because it appears our bitcoind download process on travis is also failing (entirely separate phenomenon which has cropped up at the same time). I checked also that with pytest 5.3.5 this PR is passing.

[AdamISZ]

So after looking at this a bit more, I think it's not necessary to do this before #536 , and is more work that way.

Reasoning: apart from about 3 template changes (struct.pack no "b", iteritems->items, removal of "future"), everything substantial is changes in jmbitcoin, and the vast majority of that code is deleted, and even in a few other cases I've already simplified/removed conversions that you're editing here. The template-like changes in jmclient can easily be added later.

Sorry, realise this kind of thing is rather annoying but given how much work #536 has been, I don't think it makes sense to interrupt it with a potentially confusing rebase for a fairly minor change, that will need a whole new round of testing and analysis in case something is off.

[jameshilliard]

the vast majority of that code is deleted

I assumed that would make it relatively easy to rebase #536 on top of this. Once #536 is merged I can rebase this PR fairly easily anyways, I just figured removing the last of the python future weirdness would simplify testing of #536.

[AdamISZ]

I just figured removing the last of the python future weirdness would simplify testing of #536.

Yes that's a reasonable thought, and thank you, but it's now kinda all done anyway.

[AdamISZ]

Closing this on the basis that it's made redundant by #536 (although many thanks for correcting errors there as you have done).