GHC version 7.8.1 has been deprecated because of a serious bug.
We'll have version 7.8.2 out soon.

http://www.haskell.org/pipermail/ghc-devs/2014-April/004605.html
http://www.haskell.org/pipermail/ghc-devs/2014-April/004616.html
haskell-parsers: add version 0.11
haskell-statistics: add version 0.11.0.0
haskell-active: update to version 0.1.0.12
haskell-cereal-conduit: update to version 0.7.2.1
haskell-diagrams-contrib: update to version 1.1.1.3
haskell-diagrams-lib: update to version 1.1.0.6
haskell-diagrams-postscript: update to version 1.0.2.3
haskell-dual-tree: update to version 0.2.0.2
haskell-hxt-unicode: update to version 9.0.2.2
haskell-hxt: update to version 9.3.1.4
haskell-monad-logger: update to version 0.3.6
haskell-monoid-extras: update to version 0.3.3.2
haskell-texmath: update to version 0.6.6.1
haskell-yesod-core: update to version 1.2.12
haskell-HTTP: update to version 4000.2.12
haskell-haskell-src: add version 1.0.1.6
haddock: update to version 2.14.2
haskell-yesod-auth: mark build as 'broken' for GHC 7.8.1

https://github.com/yesodweb/yesod/issues/713