WalletLocked exceptions in beempy?

Been struggling with some code for reviving the Silent Bob curation on creativecoin in a few months. While I'm not a huge fan of synchronous python, I decided on beempy for the Hive account@silentbot bot. Tracing the curation commands on the chain works just fine, but when I try to take some actual action using the posting key of the bot, I keep getting WalletLocked exceptions. But I'm not using a wallet, just the posting key, because I want my bot to be running in docker on my NAS.

I hope maybe someone in the HiveDevs community can help me out to get this working.

In the constructor of my bot I'm doing something like this:

class SilentBot:
    def __init__(self, wif, rewind=5):
        self.stm = Hive(node="https://api.hive.blog", keys=[wif])
        self.account = Account(self.stm.wallet.getAccountFromPrivateKey(wif))
        ...

Then, later in my code:

    def star(self, author, permlink, star_count):
        comment = Comment("@" + author + "/" + permlink)
        power_up = (comment.json()["percent_hbd"] == 0)
        if star_count > 5:
            star_count = 5
        if star_count < 1:
            star_count = 1
        config = self.lookup[power_up][star_count]
        body = ' + config["link"] + '"> + config["icon"] + '">'
        comment.reply(body=body, author=self.account)
        print("STAR", star_count, power_up, author, permlink, config["percentage"])
        self.vote_queue.append([config["percentage"], author, permlink])

At the moment comment.reply gets called I end up with a WalletLocked exception:

BLOCK: 59453240
BLOCK: 59453241
Traceback (most recent call last):
  File "./silentbot.py", line 141, in <module>
    bot.run()
  File "./silentbot.py", line 129, in run
    count = self.upto_head()
  File "./silentbot.py", line 111, in upto_head
    self.invocation(vals["parent_author"], vals["parent_permlink"], vals["body"])
  File "./silentbot.py", line 90, in invocation
    return self.star(author, permlink, star_count)
  File "./silentbot.py", line 75, in star
    comment.reply(body=body, author=self.account)
  File "/home/rob-install/.local/lib/python3.6/site-packages/beem/comment.py", line 785, in reply
    reply_identifier=self.identifier)
  File "/home/rob-install/.local/lib/python3.6/site-packages/beem/blockchaininstance.py", line 2022, in post
    return self.finalizeOp(ops, account, "posting", **kwargs)
  File "/home/rob-install/.local/lib/python3.6/site-packages/beem/blockchaininstance.py", line 935, in finalizeOp
    self.txbuffer.appendSigner(account, permission)
  File "/home/rob-install/.local/lib/python3.6/site-packages/beem/transactionbuilder.py", line 247, in appendSigner
    raise WalletLocked()
beemstorage.exceptions.WalletLocked

Does beempy only allow replies using a wallet? Or amy I doing something stupid here, resulting in this exception ? Or is beempy, just like my own discontinued async python library considered deprecated, and should I use another Python library for my project?