Fix 'cabal test' after unpacking a tarball.

[ethercrow]

See commercialhaskell/stackage#794

[ryanartecona]

@ethercrow Do you know if the path to that file will be the same after unpacking it as a tarball vs. in development, in this repo? A quick search brought me to this section of Cabal documentation, which suggests I'll need to add some code to the tests to make sure it loads that file from the right place.

Does that sound right to you? I never know how much I can trust cabal docs verbatim.

[ryanartecona]

Then again, I suppose the best way to test would be to do an sdist and try installing it somewhere else locally.

[ethercrow]

I did a sdist, unpacked it and saw that 'cabal test' passed.

[ryanartecona]

I did too, just before you commented :). The note in that linked doc page about Cabal installing data-files into different places on different platforms made me nervous, so in 73416c3 I just went ahead and did the change suggested in the docs. If I cabal install that sdist tarball locally with run-tests: True in a cabal.config, it works just the same whether or not I include the Paths_docopt module and the getDataFileName helper, so I'd rather err on the side of trusting the docs.

The docopt-0.7.0.4 release I just uploaded includes both changes, so let's hope this one goes through without issue!