Use Python 3.8

We're still compatible with 3.7 so we don't bump python_requires for
now.

.travis.yml

@@ -1,11 +1,16 @@
-dist: xenial
-language: generic
+dist: focal
+language: python
+python:
+  - '3.7'
+  - '3.8'
 services:
   - postgresql
 addons:
-  postgresql: '10'
-before_install:
-  - pyenv local 3.7.1
+  postgresql: '12'
+  apt:
+    packages:
+      - postgresql-12
+      - postgresql-client-12
 install:
   - PYTHON=python make
 before_script:

Makefile

@@ -1,4 +1,4 @@
-PYTHON ?= python3.7
+PYTHON ?= python3.8
 FLASK_HOST ?= 127.0.0.1
 FLASK_PORT ?= 5000
 REACT_PORT ?= 3000

README.md

@@ -45,12 +45,12 @@ decided (still work in progress!).
 
 ## Development
 
-We chose Python 3.7 as the backend language, so make sure you have it installed. To prepare the development environment it is enough to run `make` which takes care of installing all required dependencies inside a new virtualenv. Typically that will be the `.venv` directory unless you override the environment variable `VENV` *e.g.* `VENV=.virtualenv make`.
+We chose Python 3.8 as the backend language, so make sure you have it installed. To prepare the development environment it is enough to run `make` which takes care of installing all required dependencies inside a new virtualenv. Typically that will be the `.venv` directory unless you override the environment variable `VENV` *e.g.* `VENV=.virtualenv make`.
 
-Make sure you have the `python3.7` binary in your PATH. You can also use the `PYTHON` environment variable to override the location of the
+Make sure you have the `python3.8` binary in your PATH. You can also use the `PYTHON` environment variable to override the location of the
 `python` binary. *e.g.:*
 ```bash
-$ PYTHON=/usr/bin/python3.7 make
+$ PYTHON=/usr/bin/python3.8 make
 ```
 
 ## Database schema

pyproject.toml

@@ -1,5 +1,5 @@
 [tool.black]
-target_version = ['py37']
+target_version = ['py38']
 skip-string-normalization = true
 exclude = '''
 (