merging PR Chaosthebot#497: Implementing the DB stuff

Chaosthebot#497: Implementing the DB stuff

Description:
This introduces the database into chaosbot. Currently on my fork, the issue commands and meritocracy tables are implemented and working, and those are provided with this PR.

The API for the database ORM is pretty simple. See [here](http://docs.peewee-orm.com/en/latest/peewee/quickstart.html) for a quickstart to doing various operations.

Hope you all enjoy! This took a surprising amount of work to get implemented.

:white_check_mark: PR passed with a vote of 11 for and 1 against, a weighted total of 10.0 and a threshold of 6.5, and a current meritocracy review.

Vote record:
@Leigende: 1
@PlasmaPower: 1
@Swizz: 1
@andrewda: 1
@anythingbot: -1
@e-beach: 1
@ike709: 1
@JustynC7: 1
@mark-i-m: 1
@md678685: 1
@rhengles: 1
@rudehn: 1

chaos.py

@@ -59,6 +59,7 @@ def main():
 
     logging.getLogger("requests").propagate = False
     logging.getLogger("sh").propagate = False
+    logging.getLogger("peewee").propagate = False
 
     log = logging.getLogger("chaosbot")
 

cron/poll_pull_requests.py

@@ -3,7 +3,7 @@
 import os
 import sys
 from os.path import join, abspath, dirname
-from lib.db import DB
+from lib.db.models import MeritocracyMentioned
 
 import settings
 import github_api as gh
@@ -16,18 +16,6 @@
 def poll_pull_requests(api):
     __log.info("looking for PRs")
 
-    db = DB.get_instance()
-
-    try:
-        db.query("""
-CREATE TABLE IF NOT EXISTS meritocracy_mentioned (
-    id INTEGER PRIMARY KEY,
-    commit_hash VARCHAR(40)
-)
-        """)
-    except:
-        __log.exception("Failed to create meritocracy mentioned DB table")
-
     # get voting window
     base_voting_window = gh.voting.get_initial_voting_window()
 
@@ -90,12 +78,11 @@ def poll_pull_requests(api):
                     # check if we need to mention the meritocracy
                     try:
                         commit = pr["head"]["sha"]
-                        if not db.query("SELECT * FROM meritocracy_mentioned WHERE commit_hash=?",
-                                        (commit,)):
+
+                        mm, created = MeritocracyMentioned.get_or_create(commit_hash=commit)
+                        if created:
                             meritocracy_mentions = meritocracy - {pr["user"]["login"].lower(),
                                                                   "chaosbot"}
-                            db.query("INSERT INTO meritocracy_mentioned (commit_hash) VALUES (?)",
-                                     (commit,))
                             gh.comments.leave_meritocracy_comment(api, settings.URN, pr["number"],
                                                                   meritocracy_mentions)
                     except: