adds python 3.7 compatibility

[benjamin-salchow]

I upgraded to Python 3.7 and I could not run your plug-in.

I got the following error: "Plugin Printer Stats (2.0.2) is not compatible to Python 3.7.3 (compatibility string: >=2.7,<3)."

So I just added the plugin_pythoncompat information and run this plugin. I had a big issue with numpy under Raspbian even with a fresh installation:

ImportError: Unable to import required dependencies:
numpy:
IMPORTANT: PLEASE READ THIS FOR ADVICE ON HOW TO SOLVE THIS ISSUE!
Importing the numpy c-extensions failed.
- Try uninstalling and reinstalling numpy.
- If you have already done that, then:
  1. Check that you expected to use Python3.7 from "/home/octopi/OctoPrint/venv/bin/python",
     and that you have no directories in your PATH or PYTHONPATH that can
     interfere with the Python and numpy version "1.18.1" you're trying to use.
  2. If (1) looks fine, you can open a new issue at
     https://github.com/numpy/numpy/issues.  Please include details on:
     - how you installed Python
     - how you installed numpy
     - your operating system
     - whether or not you have multiple versions of Python installed
     - if you built from source, your compiler versions and ideally a build log
- If you're working with a numpy git repository, try `git clean -xdf`
  (removes all files not under version control) and rebuild numpy.
Note: this error has many possible causes, so please don't comment on
an existing issue about this - open a new one instead.
Original error was: libf77blas.so.3: cannot open shared object file: No such file or directory

I had to install a package for numpy to work correctly:

apt install libatlas-base-dev

Without that package it won't work and run always into the numpy error.

Now it works like a charm with Python 3.7.3 and I had no issue with my OctoPrint setup.

[benjamin-salchow]

@amsbr could you please take a look at it :-)?

[IIAIronWolf]

This is a pretty important plugin for my printer. Hopefully the author responds soon.

[ciordia9]

Glad I checked this out. Your method worked for me. Nothing core needing upgrading luckily so that made it pretty easy. Thanks for trying/doing/validating it!

[AlexVerrico]

G'Day @benjamin-salchow
I have mirrored this repo and will be taking over maintenance of this plugin.
It would be great if you could make your PR against the python3-compat branch over at https://github.com/AlexVerrico/octoprint-stats/tree/python3-compat
Cheers, Alex.

[AlexVerrico]

Also if you want to chat further about it, feel free to join https://gitter.im/AlexVerricoChat/octoprint-stats

[benjamin-salchow]

Hello Alex, sounds great. I'll create the pull request at the new repository in some minutes :-).

[AlexVerrico]

Sounds good.