If you write 'library pkgname' you get a bad error on new-build

```
ezyang@sabre:~/Dev/labs/T4081$ /srv/code/cabal-tmp/dist-newstyle/build/x86_64-linux/ghc-7.10.3/cabal-install-1.25.0.0/noopt/build/cabal/cabal new-build -j4
Resolving dependencies...
toConfiguredComponent: p p
```

This is with `library p` in a package named `p`.