no need to hide 'catch'

This doesn't normally cause a problem because of some ghc workaround special to this case, but I was able to trigger an error with a complicated mixture of sandboxing, directing `cabal` to a locally installed ghc, and something else. `catch` isn't actually used in the file, so it seems it might as well go.
Merge pull request #1309 from michaelt/patch-1

no need to hide 'catch'