`sign(...)` in `sr25519` requires randomness

[puzzle-rusher]

Is there an existing issue?

• [X] I have searched the existing issues

Description of bug

When I tried to use sr25519::Pair::sign function from sp-core with default-features = false, features = ["full_crypto"] I ran into an error like

thread 'delegated_approve_success' panicked at 'Attempted to use functionality that requires system randomness!!', .../schnorrkel-0.9.1/src/lib.rs:244:55

Then I added "getrandom" in the sp-core's cargo.toml and added rand to full_crypto dependencies and it started working.

Maybe I did something wrong, please give me a solution to this problem.

If there are no hacks here, I suggest two solutions, to do something like above or remove sign function from full_crypto feature.