Better Debug encoding for Binary

[ethanfrey]

When debugging message calls, I get hard to read output like:

Execute { contract_addr: "Contract #1", msg: Binary([123, 34, 101, 120, 101, 99, 117, 116, 101, 34, 58, 123, 34, 99, 111, 110, 116, 114, 97, 99, 116, 95, 97, 100, 100, 114, 34, 58, 34, 67, 111, 110, 116, 114, 97, 99, 116, 32, 35, 50, 34, 44, 34, 109, 115, 103, 34, 58, 34, 101, 51, 48, 61, 34, 44, 34, 102, 117, 110, 100, 115, 34, 58, 91, 93, 125, 125]), funds: [] }

This is the Debug encoding of Binary and it should be improved from default. I have two ideas:

1. Always hex-encode it (which is more debug friendly than base64... some of us can read ascii bytes in hex)
2. If ASCII printable, encode it as a string. Otherwise prefix 0x and hex-encode (as 1)

Approach 2 is not very stable for any APIs you would depend on, but debug is only meant for test output for developers, so let's make this nice.

[webmaster128]

1. is cool and solid. Happy to implement.

The big question is to what degree that change would violate stability promises.

[ethanfrey]

I am quite sure we never use Debug outside of test code.
We already have a custom Display implementation which uses base64, which might escape into some contract APIs.

I would not change display, only a Debug implementation which is just for unit tests.