troll.py

import praw

client_id = 'XXXX'
client_secret = 'XXXX'
reddit_user = 'XXXX'
reddit_pass = 'XXXX'
user_agent = 'Troll thing'
target_user = 'XXXX'

reply = 'Go spam someone else with your idiotic bullshit please.'

reddit = praw.Reddit(client_id=client_id,
                     client_secret=client_secret,
                     user_agent=user_agent,
                     username=reddit_user,
                     password=reddit_pass)


for msg in reddit.inbox.stream():
    body = msg.body
    author = msg.author.name
    if author == target_user:
        print(body)
        msg.reply(reply)