Re: [BuildStream] Dropping support for Python 3.5 in master

[Chandan Singh <chandan chandansingh net>]

Hi Jürg,

Strong +1 from my side.

> All of the latest Linux LTS distro versions support Python 3.6 or
> later. Ubuntu 18.04 LTS and SLES 15 include Python 3.6, Debian 10
> (current stable) includes Python 3.7. RHEL/CentOS 7 support Python 3.6
> via SCL (no Python 3 at all in the main repository). In RHEL/CentOS 8,
> Python 3.6 is the default.
>
> Upstream end-of-life of Python 3.5 is scheduled for 2020-09-13¹.

On a related note, our sibling project BuildGrid has dropped support
for Python 3.5 already.

> New features in Python 3.6 that could be useful:
> * PEP 498: f-strings
> * PEP 526: Type annotations for variables
> * PEP 525: Asynchronous generators (and asyncio is now stable)
> * PEP 519: File system path protocol

I'm especially looking forward to being able to use proper type hints
and variables, and get rid of all the `# type` comments I had to do
initially.

Cheers,
Chandan