cashu requires python-bitcoinlib which makes extension unusable in LNbits

[prusnak]

Transfered from https://github.com/lnbits/lnbits/pull/2044 here

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Currently cashu extension is broken in LNbits, because it requires python-bitcoinlib which is not imported (not present in LNbits pyproject.toml).

Relevant code that uses python-bitcoinlib is here: https://github.com/lnbits/cashu/blob/0.3.0/lib/cashu/core/script.py#L9-L18

We can either: 1) rewrite the code to use embit instead of python-bitcoinlib (embed is imported by LNbits by default because other 3 dependencies need it) 2) copy required code from python-bitcoinlib to cashu repo (what boltz extension does with boltz_client dependency) 3) identify whether the code in lib/cashu/core/script.py is needed in LNbits context and if not, fix it so it's not imported there

[callebtc]

Fixed by #45 (removed python-bitcoinlib)