This involves hacking the code used to run cargo test on various
packages, because it reads Cargo.lock to determine which packages should
be tested. This change implements a blacklist, since that will catch new
crates when they are added in the future.
Automated conversion using the untry tool [1] and the following command:
```
$ find -name '*.rs' -type f | xargs untry
```
at the root of the Rust repo.
[1]: https://github.com/japaric/untry
