If the ordering doesn't matter, we can avoid the annoying `list()` to expand a generator using something like:
```
    expected_hashes[req.name] = []
    for hash_ in hashes_above(path, line_number):
        expected_hashes[req.name].append(hash_)
missing_hashes = [k for k in k, v in expected_hashes.items() where not v]
```