feat: Move vcs backend to asyncio

The core goal here is to resolve some IO latency/blocking in vcs-server when `git fetch` takes a long period of time.

This upgrades us to Python 3.8.1 as well to make use of AsyncMock.

Note, pytest is locked at <5.4 right now, and is currently broken as of the 5.4.0 release.

Author: dcramer

.pre-commit-config.yaml

@@ -4,7 +4,7 @@ repos:
     rev: 18.6b4
     hooks:
     - id: black
-      language_version: python3.7
+      language_version: python3.8
 -   repo: git://github.com/pre-commit/pre-commit-hooks
     rev: v2.0.0
     hooks:
@@ -19,10 +19,10 @@ repos:
     - id: no-commit-to-branch
     - id: trailing-whitespace
     - id: debug-statements
-      language_version: python3.7
+      language_version: python3.8
     - id: flake8
       log_file: '.artifacts/flake8.log'
-      language_version: python3.7
+      language_version: python3.8
     - id: requirements-txt-fixer
       args: ['requirements-base.txt', 'requirements-dev.txt', 'requirements-test.txt']
 # -   repo: https://github.com/pre-commit/mirrors-mypy

.python-version

@@ -1,2 +1,2 @@
-3.7.2
+3.8.1
 2.7.14

.travis.yml

@@ -4,12 +4,12 @@ branches:
     - trying
 language: python
 sudo: true
-dist: xenial
+dist: buster
 services:
   - redis-server
   - postgresql
 python:
-  - '3.7'
+  - '3.8'
 cache:
   yarn: true
   directories:

Dockerfile

@@ -1,5 +1,5 @@
 # Use an official Python runtime as a parent image
-FROM python:3.7-slim-stretch
+FROM python:3.8.2-slim-buster
 
 # add our user and group first to make sure their IDs get assigned consistently
 RUN groupadd -r zeus && useradd -r -m -g zeus zeus
@@ -29,6 +29,7 @@ RUN set -ex \
   libpq-dev \
   libxml2-dev \
   libxslt-dev \
+  libz-dev \
   openssl \
   ssh \
   wget \

Makefile

@@ -5,7 +5,7 @@ upgrade: install-requirements
 	poetry run zeus db upgrade
 
 setup-git:
-	pip install "pre-commit>=1.12.0,<1.13.0"
+	pip install "pre-commit>=2.2.0,<2.3.0"
 	pre-commit install
 	git config branch.autosetuprebase always
 	git config --bool flake8.strict true

README.md

@@ -76,7 +76,7 @@ They should be submitted with the `application/x-webpack-stats+json` type.
 
 ### Requirements
 
-- Python 3.7
+- Python 3.8
 - Node (and [Volta](https://volta.sh/))
 - Postgres 9.4+