set the minimum supported version at py35

[mmerickel]

I could use some help finishing this out. Need to track down other places (probably in the docs and tutorials) that python versions are referenced.

[stevepiercy]

Changes look good so far, with a couple of corrections.

I will scan the docs and make a PR to your branch.

[stevepiercy]

By dropping 3.5, we need to revise our Python support policy.

But first the wording is kind of klunky.

At the time of a Pyramid version release, each supports all versions of Python
through the end of their lifespans.

I think the intent was:

When a major version of Pyramid is released, it is supported to work on each active version of Python at that time through the end of its lifespan.

And finally, perhaps add a sentence?

For the Pyramid 2.0 release, an exception was made to that policy to drop support of Python 3.5 ahead of its end-of-life date.
[Insert optional reasons here.]

[stevepiercy]

I found this while scanning for 3.5. Candidate for removal?

pyramid/src/pyramid/config/actions.py

Lines 562 to 567 in 497e667

	# Work around a Python 3.5 issue whereby it would insert an
	# extra stack frame. This should no longer be necessary in
	# Python 3.5.1
	last_frame = ActionInfo(*f[-1])
	if last_frame.function == 'extract_stack': # pragma: no cover
	f.pop()

[mmerickel]

I’m fine with keeping 3.5 if we have docs around it. There aren’t 3.6 specific features yet. If we were doing more with typing then there might be good reason.

[stevepiercy]

The docs don't need 3.5. There were a couple mentions that we support 3.5, and that was it. When I last updated the docs, I bumped up almost everything to 3.7.

I think the choice is whether you want to open the door to 3.6 features or have 3.5 block their implementation.

[mmerickel]

By dropping 3.5, we need to revise our Python support policy.

I don't really want to make an exception for 3.6. If our policy is to support 3.5 then we should support 3.5.

[mmerickel]

the failing CI is around an unrelated issue with cookiecutter