ghc-pkg command fails

I have a Cabal file that fails with:

```
In-place registering hsbag-0.1.0.0...
setup-Simple-Cabal-1.22.1.1-x86_64-linux-ghc-7.8.3: '/usr/local/bin/ghc-pkg'
exited with an error:
hsbag-0.1.0.0: Warning: Unrecognized field data-dir on line 15
hsbag-0.1.0.0: Warning: Unrecognized field key on line 4
hsbag-0.1.0.0: Warning: haddock-interfaces:
/home/omer/opt/libcds_b629/haskell/dist/dist-sandbox-fa1c82ae/doc/html/hsbag/hsbag.haddock
doesn't exist or isn't a file
hsbag-0.1.0.0: Warning: haddock-html:
/home/omer/opt/libcds_b629/haskell/dist/dist-sandbox-fa1c82ae/doc/html/hsbag
doesn't exist or isn't a directory
```

I have no ideas why it's looking for documentation file. This is happening even if I use `--disable-documentation`.

Start by reproducing the Cabal in-place registration failure using the reported hsbag-0.1.0.0 output and the --disable-documentation option. Investigate why ghc-pkg processes the haddock-interfaces and haddock-html fields; done means registration no longer fails when those documentation paths are absent or documentation is disabled.

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