[scikit-image] Minimum Python version?

[Stefan van der Walt]

On Tue, 26 Jun 2018 17:11:25 +1000, Juan Nunez-Iglesias wrote:
> What Python version do we want for 0.15? Currently, it is set to 3.5. I
> want to make a motion for 3.6. This gives us:
> - f-strings, which is super nice syntax.
> - dictionaries maintain insertion order, which is also super nice. (We
>   would be able to replace all OrderedDict instances with plain
> dicts.)

Features are nice (very nice, in this case) to have, but in itself is
not a good enough reason to switch.

Let's look at our installation statistics:

$ pypinfo skimage pyversion

| python_version | download_count |
| -------------- | -------------- |
| 3.6            |          3,172 |
| 2.7            |          1,995 |
| 3.5            |          1,866 |
| 3.4            |            118 |
| None           |             85 |
| 3.7            |             18 |

It looks like 3.5 currently makes up about 37% of Python 3 installs.
This number should come down over the next few months, but I suggest we
keep supporting 3.5 for at least one more release.

Also, note the 18 installs on 3.7.  We should get ready!

Best regards,
Stéfan