Produces an error like:
```
; KUMOD_LOG=kumod=info ./target/debug/kumod --policy simple_policy.lua
2023-05-16T18:16:02.112017Z INFO main kumod::memory: using limits: soft=Some("101.22 GB"), hard=Some("134.96 GB")
Error: callback error
stack traceback:
[C]: in function 'kumo.on'
[string "simple_policy.lua"]:232: in main chunk
caused by: smtp_server_auth_plain event already has a handler defined at simple_policy.lua:226
```
Wez Furlong
536827db99