Resolving dependencies...
Configuring caf-0.0.2...
Building caf-0.0.2...
Failed to install caf-0.0.2
Build log ( /home/builder/.cabal/logs/caf-0.0.2.log ):
cabal: Entering directory '/tmp/cabal-tmp-6183/caf-0.0.2'
Configuring caf-0.0.2...
Building caf-0.0.2...
Preprocessing library caf-0.0.2...
[1 of 7] Compiling Control.Concurrent.Futures.Futures ( Control/Concurrent/Futures/Futures.hs, dist/build/Control/Concurrent/Futures/Futures.o )
[2 of 7] Compiling Control.Concurrent.Futures.Buffer ( Control/Concurrent/Futures/Buffer.hs, dist/build/Control/Concurrent/Futures/Buffer.o )
[3 of 7] Compiling Control.Concurrent.Futures.Chan ( Control/Concurrent/Futures/Chan.hs, dist/build/Control/Concurrent/Futures/Chan.o )

Control/Concurrent/Futures/Chan.hs:22:12: warning: [-Wtabs]
    Tab character found here, and in 7 further locations.
    Please use spaces instead.
[4 of 7] Compiling Control.Concurrent.Futures.HQSem ( Control/Concurrent/Futures/HQSem.hs, dist/build/Control/Concurrent/Futures/HQSem.o )

Control/Concurrent/Futures/HQSem.hs:17:1: warning: [-Wtabs]
    Tab character found here, and in 17 further locations.
    Please use spaces instead.
[5 of 7] Compiling Control.Concurrent.Futures.QSem ( Control/Concurrent/Futures/QSem.hs, dist/build/Control/Concurrent/Futures/QSem.o )

Control/Concurrent/Futures/QSem.hs:19:1: warning: [-Wtabs]
    Tab character found here, and in 13 further locations.
    Please use spaces instead.
[6 of 7] Compiling Control.Concurrent.Futures.BChan ( Control/Concurrent/Futures/BChan.hs, dist/build/Control/Concurrent/Futures/BChan.o )
[7 of 7] Compiling Control.Concurrent.Futures ( Control/Concurrent/Futures.hs, dist/build/Control/Concurrent/Futures.o )

Control/Concurrent/Futures.hs:70:1: error:
    Failed to load interface for ‘Control.Concurrent.Futures.Barrier’
    Use -v to see a list of the files searched for.
cabal: Leaving directory '/tmp/cabal-tmp-6183/caf-0.0.2'
cabal: Error: some packages failed to install:
caf-0.0.2 failed during the building phase. The exception was:
ExitFailure 1