#16083 has been abandoned, so it would be a good first issue to take the branch (bitcoin/bitcoin#16083 (comment)) and submit it as a new pull request.

Useful skills:

Understanding of undo data, the RPC interface and the functional tests.

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The purpose of the good first issue label is to highlight which issues ar

Split the code from create_sandbox into two separate functions and remove the noqa: C901.

Describe alternatives you've considered
Simplify the function such that no split is required.

Additional context
Code quality:

2020-04-29T13:13:32.5968940Z ./syft/sandbox.py:12:1: C901 'create_sandbox' is too complex (26)
2020-04-29T13:13:32.5969257Z def create_sandbox(gbs, 

The blockchain v2 reactor utilizes concurrency to saturate the bottleneck of writing blocks to disk. This concurrency is internal to the reactor where the reactor itself will launch and manage internal state machines running as go-routines. This configuration makes testing difficult as we don't know when messages processed by internal state machines will be processed and when we can assert that th