Bump minimum Python version to 3.7 (#302)

Author: ataffanel

.github/workflows/dependency_check.yml

@@ -17,10 +17,10 @@ jobs:
       - name: install lib
         run: pip install -e .
 
-  minimum-python:
+  minimum-python37:
     runs-on: ubuntu-latest
     container:
-      image: python:3.6
+      image: python:3.7
 
     steps:
       - uses: actions/checkout@v2

docs/installation/install.md

@@ -3,6 +3,10 @@ title: Installation
 page_id: install
 ---
 
+## Requirements
+
+This project requires Python 3.7+.
+See below sections for more platform-specific requirements.
 ## Development
 ### Developing for the cflib
 * [Fork the cflib](https://help.github.com/articles/fork-a-repo/)
@@ -12,7 +16,7 @@ page_id: install
 
 * [Uninstall the cflib if you don't want it any more](http://pip-python3.readthedocs.org/en/latest/reference/pip_uninstall.html), `pip uninstall cflib`
 
-Note: If you are developing for the cflib you must use python3. On Ubuntu (16.04, 18.08) use `pip3` instead of `pip`.
+Note: If you are developing for the cflib you must use python3. On Ubuntu (20.04+) use `pip3` instead of `pip`.
 
 ### Linux, OSX, Windows