fixed error message and cleaned up code

[sourcery-ai[bot]]

Sourcery Code Quality Report

❌  Merging this PR will decrease code quality in the affected files by 0.61%.

Quality metrics	Before	After	Change
Complexity	4.00 ⭐	4.28 ⭐	0.28 👎
Method Length	84.88 🙂	85.91 🙂	1.03 👎
Working memory	7.40 🙂	7.46 🙂	0.06 👎
Quality	67.55% 🙂	66.94% 🙂	-0.61% 👎

Other metrics	Before	After	Change
Lines	1445	1445	0

Changed files	Quality Before	Quality After	Quality Change
btclib/bip32/bip32.py	65.51% 🙂	63.21% 🙂	-2.30% 👎
btclib/ec/curve_group.py	69.45% 🙂	69.45% 🙂	0.00%
tests/bip32/test_bip32.py	66.55% 🙂	66.55% 🙂	0.00%

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
btclib/bip32/bip32.py	BIP32KeyData.assert_valid	21 😞	304 ⛔	11 😞	32.58% 😞	Refactor to reduce nesting. Try splitting into smaller methods. Extract out complex expressions
btclib/ec/curve_group.py	CurveGroup.__init__	13 🙂	224 ⛔	11 😞	42.48% 😞	Try splitting into smaller methods. Extract out complex expressions
btclib/ec/curve_group.py	_multi_mult	11 🙂	202 😞	12 😞	44.01% 😞	Try splitting into smaller methods. Extract out complex expressions
btclib/bip32/bip32.py	_derive	16 🙂	164 😞	8 🙂	50.90% 🙂	Try splitting into smaller methods
btclib/ec/curve_group.py	CurveGroup.add_jac	2 ⭐	201 😞	11 😞	54.44% 🙂	Try splitting into smaller methods. Extract out complex expressions

Legend and Explanation

The emojis denote the absolute quality of the code:

• ⭐ excellent
• 🙂 good
• 😞 poor
• ⛔ very poor

The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

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Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Help us improve this quality report!