Code

#!/usr/bin/env python3

import praw
import sys
import os
from time import gmtime, strftime
try:
    from flair_list import flairs
except ImportError as e:
    print("Flairs file can't be accessed\n")
    print(e)
    sys.exit()
except SyntaxError as e:
    print("There is a syntax error in the flair list\n")
    print(e)
    sys.exit()


class FlairBot:

    # User agent that PRAW uses to identify your bot to reddit
    USER_AGENT = 'ubuntu:thealpacalypse.me:v1 (run by /u/tehalpacalypse)'
    # User name/password of the account that the bot will run through
    USER_NAME = ''
    PASSWD = ''

    # Blacklist for users abusing the flair system
    BLACKLIST = ['sampleuser', 'sampleUSER2']

    """ The SUBJECT will be the default subject of your PMs
    when you create the URLs, eg.

    reddit.com/message/compose/?to=some_user&subject=flair&message=some_message

    PMs require a subject, but it's also a simple way of identifying
    PMs that are directed towards the flairs and not just a general PM"""
    SUBJECT = 'flair'

    # TARGET_SUB is the name of the subreddit without the leading /r/
    TARGET_SUB = 'worldpowers'

    # Turn on output to log file in current directory - log.txt
    LOGGING = True

    # Class variable to hold the PRAW instance
    r = None

    # Class variable to hold the unread pms
    pms = None

    def init(self):
        print("Get 1")
        if self.LOGGING:
            os.chdir(os.path.dirname(os.path.abspath(__file__)))
        self.login()

    def login(self):
        """ Log in to the account being used for the bot """
        print("Get 2")
        try:
            self.r = praw.Reddit(user_agent=self.USER_AGENT)
            self.r.login(self.USER_NAME, self.PASSWD)
            self.fetch_pms()
        except:
            raise

    def fetch_pms(self):
        """ Get a listing of all unread PMs for the user account """
        print("Get 3")
        self.pms = self.r.get_unread(limit=None)
        if self.pms is not None:
            self.process_pms()

    def process_pms(self):
        print("Get 4")
        i = 0
        for pm in self.pms:
            i = i + 1
            print("PM #", i)
            if str(pm.subject) == self.SUBJECT:
                print("Get 4.1")
                author = str(pm.author)  # Author of the PM
                if author.lower() in (user.lower() for user in self.BLACKLIST):
                    print("Get 4.2")
                    continue
                content = str(pm.body)  # Content of the PM
                index = content.find(":")
                if index != -1:
                    print("Get 4.3")
                    continue
                newflair = content[:index].strip()# Substrings the PM to get flair only
                subreddit = self.r.get_subreddit(self.TARGET_SUB)
                print("Get 4.4")
                if newflair in flairs:
                    print("Get 4.5")
                    # Get the flair text that corresponds with the class name
                    flair_text = content[index + 1:].strip()
                    subreddit.set_flair(author, flair_text, newflair)
                    if self.LOGGING:
                        print("Get 4.6")
                        self.log(author, content, flair_text, newflair)
                pm.mark_as_read()  # Mark processed PM as read

    def log(self, author, content, flair_text, newflair):
        print("Get 5")
        with open('log.txt', 'a', encoding="UTF-8") as logfile:
            time_now = strftime("%Y-%m-%d %H:%M:%S", gmtime())
            log_text = 'Added: ' + author + ' : ' \
                + flair_text + ' : ' \
                + newflair + ' @ ' + time_now + ' EST\n'
            logfile.write(log_text)
FlairBot().init()

Output

Get 1
Get 2
Get 3
Get 4
PM # 1
Get 4.1
Get 4.3
PM # 2
Get 4.1
Get 4.3
PM # 3
Get 4.1
Get 4.3
PM # 4
Get 4.1
Get 4.3
PM # 5
Get 4.1
Get 4.3
PM # 6
Get 4.1
Get 4.3
PM # 7
Get 4.1
Get 4.3
PM # 8
Get 4.1
Get 4.3
PM # 9
Get 4.1
Get 4.3
PM # 10
Get 4.1
Get 4.3
PM # 11
Get 4.1
Get 4.3
PM # 12
Get 4.1
Get 4.3
PM # 13
Get 4.1
Get 4.3
PM # 14
Get 4.1
Get 4.3
PM # 15
Get 4.1
Get 4.3
PM # 16
Get 4.1
Get 4.3
PM # 17
Get 4.1
Get 4.3
PM # 18
Get 4.1
Get 4.3
PM # 19
Get 4.1
Get 4.3
PM # 20
Get 4.1
Get 4.3
PM # 21
Get 4.1
Get 4.3
PM # 22
Get 4.1
Get 4.3
PM # 23
Get 4.1
Get 4.3
PM # 24
Get 4.1
Get 4.3
PM # 25
Get 4.1
Get 4.3
PM # 26
Get 4.1
Get 4.3
PM # 27
Get 4.1
Get 4.3
PM # 28
Get 4.1
Get 4.3
PM # 29
Get 4.1
Get 4.3
PM # 30
Get 4.1
Get 4.3
PM # 31
Get 4.1
Get 4.3
PM # 32
Get 4.1
Get 4.3
PM # 33
Get 4.1
Get 4.3
PM # 34
Get 4.1
Get 4.3
PM # 35
Get 4.1
Get 4.3
PM # 36
Get 4.1
Get 4.3
PM # 37
Get 4.1
Get 4.3
PM # 38
Get 4.1
Get 4.3
PM # 39
Get 4.1
Get 4.3
PM # 40
Get 4.1
Get 4.3
PM # 41
Get 4.1
Get 4.3
PM # 42
Get 4.1
Get 4.3
PM # 43
Get 4.1
Get 4.3
PM # 44
Get 4.1
Get 4.3
PM # 45
Get 4.1
Get 4.3
PM # 46
Get 4.1
Get 4.3
PM # 47
Get 4.1
Get 4.3
PM # 48
Get 4.1
Get 4.3
PM # 49
Get 4.1
Get 4.3
PM # 50
Get 4.1
Get 4.3
PM # 51
Get 4.1
Get 4.3
PM # 52
Get 4.1
Get 4.3
PM # 53
Get 4.1
Get 4.3
PM # 54
Get 4.1
Get 4.3
PM # 55
Get 4.1
Get 4.3
PM # 56
Get 4.1
Get 4.3
PM # 57
Get 4.1
Get 4.3
PM # 58
Get 4.1
Get 4.3
PM # 59
Get 4.1
Get 4.3
PM # 60
Get 4.1
Get 4.3
PM # 61
Get 4.1
Get 4.3
PM # 62
Get 4.1
Get 4.3
PM # 63
Get 4.1
Get 4.3
PM # 64
Get 4.1
Get 4.3
PM # 65
Get 4.1
Get 4.3
PM # 66
Get 4.1
Get 4.3
PM # 67
Get 4.1
Get 4.3
PM # 68
Get 4.1
Get 4.3
PM # 69
Get 4.1
Get 4.3
PM # 70
Get 4.1
Get 4.3
PM # 71
Get 4.1
Get 4.3
PM # 72
Get 4.1
Get 4.3
PM # 73
Get 4.1
Get 4.3
PM # 74
Get 4.1
Get 4.3
PM # 75
Get 4.1
Get 4.3
PM # 76
Get 4.1
Get 4.3
PM # 77
Get 4.1
Get 4.3
PM # 78
Get 4.1
Get 4.3
PM # 79
Get 4.1
Get 4.3