ERRBOT crash after flooded command DM.

[Rixxan]

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I am...

• Reporting a bug
• Suggesting a new feature
• Requesting help with running my bot
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• Here about something else

I am running...

• Errbot version: 6.1.5
• OS version: Ubuntu 20.04 LTS
• Python version: 3.8
• Using a virtual environment: yes

Issue description

Spamming the bot with "!whoami" or other similar commands in DMs causes the bot to quit with a READ ERROR in IRC (client crash), and forces errbot reinstallation.

Attempts to manually start errbot return `_gdbm.error: [Errno 11] Resource temporarily unavailable: '/home/ubuntu/pyProjects/errbot/data/repomgr.db'.

Steps to reproduce

Launch errbot (with IRC backend)
Join server
Open DM to errbot
Spam !whoami or !about until bot quits with READ ERROR (indicating system crash)

Additional info

Live logs have information about SSL : BAD LENGTH (ValueError: Write on closed or unwrapped SSL socket.) that comes into play during the crash and spam.

Pastebin: https://pastebin.com/8Jspytf8

Rate Limiting in Conf is set to 2 seconds for private messages, however, I don't know if this could be related.