Resolving dependencies...
Configuring darcs-2.4.3...
Failed to install darcs-2.4.3
Build log ( /home/builder/.cabal/logs/darcs-2.4.3.log ):
cabal: Entering directory '/tmp/cabal-tmp-21133/darcs-2.4.3'
cabal: Leaving directory '/tmp/cabal-tmp-21133/darcs-2.4.3'
cabal: Error: some packages failed to install:
darcs-2.4.3 failed during the configure step. The exception was:
user error ('/opt/ghc/8.0.2/bin/ghc' exited with an error:

/tmp/cabal-tmp-21133/darcs-2.4.3/Distribution/ShellHarness.hs:13:1: error:
Failed to load interface for ‘System’
Use -v to see a list of the files searched for.

/tmp/cabal-tmp-21133/darcs-2.4.3/Distribution/ShellHarness.hs:21:1: error:
Failed to load interface for ‘Control.OldException’
Perhaps you meant Control.Exception (from base-4.9.0.0)
Use -v to see a list of the files searched for.
)