Cannot create several tests

[NinoLipartiia4ire]

If you try running several separate tests with a sandboxed environment for the first time, at least one of them fails.

See an example: NinoLipartiia4ire/workspaces-rs-example@33a479d.
Both tests from this example should pass. But if you run them:

git clone https://github.com/NinoLipartiia4ire/workspaces-rs-example
cd workspaces-rs-example/tests-workspaces-rs && cargo test

Either one of them fails:

test second_test ... ok
test first_test ... FAILED

failures:

---- first_test stdout ----
Starting up sandbox at localhost:24842
thread 'first_test' panicked at 'called `Result::unwrap()` on an `Err` value: Directory not empty (os error 66)', /Users/nino/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/workspaces-0.1.0/src/network/sandbox.rs:43:24

Or both tests fail:

test second_test ... FAILED
test first_test ... FAILED

failures:

---- second_test stdout ----
Starting up sandbox at localhost:22402
thread 'second_test' panicked at 'called `Result::unwrap()` on an `Err` value: /Users/nino/projects/issue-workspaces-rs/workspaces-rs-example/tests-workspaces-rs/target/debug/build/near-sandbox-utils-0a71fab0dd1ce1e6/out/near-sandbox-8b3f59a31cb9016b/near-sandbox is not executable', /Users/nino/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/workspaces-0.1.0/src/network/sandbox.rs:43:24
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- first_test stdout ----
Starting up sandbox at localhost:17497
thread 'first_test' panicked at 'called `Result::unwrap()` on an `Err` value: No such file or directory (os error 2)', /Users/nino/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/workspaces-0.1.0/src/network/sandbox.rs:43:24

Running cargo test for the second time and later doesn't return any error, both tests pass.

To reproduce this bug again: cargo clean && cargo test.

[ChaoticTempest]

I think I see the issue here. There was a race condition when installing the binary, so this should be fixed with this PR #46

[mikedotexe]

Given the last comment, I think I'll close this