LGTM.com - false positive "Statement has no effect" for Python await

**Description of the false positive**

The `await` expression is used to run coroutines, which by design have side-effects. However, CodeQL erroneously treats a bare `await` expression like any other bare expression and thus assumes it has no side-effects and is used in error. This leads to false-positive flags when `await` is used to trigger a side-effect without a return value.

```python3
def foo():
...
# close a critical resource
await aclose
```

**URL to the alert on the project page on ~~LGTM.com~~ GithHub**

https://github.com/maxfischer2781/asyncstdlib/security/code-scanning/9