DO NOT MERGE: travis: MORE VERSIONS

[petertseng]

No description provided.

[petertseng]

7.4 currently broken. Dependencies install fine, but:

_test/check-exercises.hs:5:27:
    Module `System.Posix.Temp' does not export `mkdtemp'

It is possible we may be able to fix it by updating the unix package.

7.2 can't resolve deps:

cabal: Could not resolve dependencies:
trying: text-1.2.2.1 (user goal)
trying: binary-0.5.0.2/installed-f86... (dependency of text-1.2.2.1)
trying: attoparsec-0.13.0.1 (user goal)
trying: scientific-0.3.4.6 (dependency of attoparsec-0.13.0.1)
rejecting: scientific-0.3.4.6:+bytestring-builder (conflict: binary =>
bytestring==0.9.2.0/installed-fe0..., scientific-0.3.4.6:bytestring-builder =>
bytestring>=0.10 && <0.11)
rejecting: scientific-0.3.4.6:-bytestring-builder (manual flag can only be
changed explicitly)
Backjump limit reached (change with --max-backjumps)

7.0 has a similar error for lens that I'm not posting all of because it's quite long.

6.12.3 has a bit of a weird error message.

cabal: dependencies conflict: ghc-6.12.3 requires an installed instance of
bytestring ==0.9.1.7 however:

it just stops there?

[petertseng]

A valiant effort to support 7.4 but ultimately unsuccessful.

The failure (again, preserved here in case Travis logs go away) is that for 7.4 and 7.6 attemping to cabal install unix will succeed, however when attempting to actually run check_exercises then we get

GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   pPrPr_disableITimers
whilst processing object file
   /home/travis/.cabal/lib/x86_64-linux-ghc-7.4.2/unix-2.7.1.0/HSunix-2.7.1.0.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

Unfortunately I do not know enough to continue, so I'll consider this experiment to have failed. Sorry.

Feel free to rerun the experiments at a later date if we change our set of dependencies (notably how check-exercises creates temporary directories), but not a battle I'm fighting now.