fix for 2347

[genos]

resolves #2347

Description

Introduction

This PR attempts to fix #2347, wherein we wish dbt to complain about trying to install with a Python version < 3.6.

Changes

Per the issue's suggestion, I found every setup.py file I could:

# If you have the fantastic `fd` utility installed:
fd setup.py
# This also works
find . -name setup.py -print

Then to each of these, I added the following after the import sys:

if sys.version_info < (3, 6):
    print('Error: dbt does not support this version of Python.')
    print('Please upgrade to Python 3.6 or higher.')
    sys.exit(1)

Testing

I used the nix package manager to attempt building this branch with both Python 2.7 and Python 3.8.

Python 2.7

Fails as expected:

~/github/test2 ∃ cat default.nix
let
  pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/20.03.tar.gz") { };
  py = pkgs.python27Full.withPackages (p: [ p.setuptools ]);
in pkgs.mkShell {
  name = "python-2-env";
  buildInputs = [ py ];
}
~/github/test2 ∃ nix-shell --pure

[nix-shell:~/github/test2]$ python ../dbt/setup.py build
Error: dbt does not support this version of Python.
Please upgrade to Python 3.6 or higher.

[nix-shell:~/github/test2]$ echo $?
1

Python 3.8

Builds just fine

~/github/test3 ∃ cat default.nix
let
  pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/20.03.tar.gz") { };
  py = pkgs.python38Full.withPackages (p: [ p.setuptools ]);
in pkgs.mkShell {
  name = "python-3-env";
  buildInputs = [ py ];
}
~/github/test3 ∃ nix-shell --pure

[nix-shell:~/github/test3]$ python ../dbt/setup.py build
running build

[nix-shell:~/github/test3]$ echo $?
0

Checklist

• [✓] I have signed the CLA
• [✓] I have run this code in development and it appears to resolve the stated issue
• [✓] This PR includes tests, or tests are not required/relevant for this PR
• [✓] I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[genos]

The latest commit (707310d) is to fix a merge conflict only in CHANGELOG.md.

[jtcohen6]

Works like a charm! Thanks so much for the contribution, @genos :) I think we can sneak this in for v0.18.0.

[jtcohen6]

Can you add a Contributors section (similar to the ones below) and include your GitHub handle + a link to this PR? We want to give you credit!

[genos]

Certainly! See 81bf3da