Serialize block count as quantity 2

[nlordell]

Sorry, there was an issue with #668

I created the PR too quickly and didn't run cargo check 🙈. It turns out there was an issue where I was moving block_count when doing block_count.into() and needed to first convert block_count to a U256 to avoid move issues.

Sorry for breaking your master builds!

PR Checklist

• Added Tests (No - but should be covered by existing tests?)
• Added Documentation (No - behaviour shouldn't have been changed)
• Updated the changelog (No - just fixes my broken PR).

Also, make sure to run check commands:

$ cargo check --all-features
$ cargo +nightly fmt --all
$ cargo build --all-features
$ cargo test --all-features

[gakonst]

7bd42be I see this is already in master?

[nlordell]

I see this is already in master?

Sorry, I got messed up and was looking at my fork. Anyway, I updated the description.

There is a build issue there where I was moving block_count on line 865 and (when calling block_count.into()) and again on line 871 when retrying (when calling block_count.into().as_u64()) but T: !Copy.

I created the PR too quickly while waiting for cargo check to finish but should have waited 🙈.