getCurrentDirectory should raise better error string when cwd doesn't exist

Run this script in a directory which no longer exists:

import System.Directory
main = getCurrentDirectory >>= putStrLn

Currently the error looks like:

ezyang@sabre:~/test$ ./test
bash: ./test: No such file or directory

It would be nicer to give a better message in this case.

Originally reported https://github.com/haskell/cabal/issues/2902

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	low
Resolution	Unresolved
Component	libraries/directory
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