Build Cabal/cabal-install with '-Werror' on Travis.

Also fix some warnings to make it work.

.travis.yml

@@ -27,14 +27,14 @@ script:
  - mkdir -p ./dist/setup
  - cp Setup.hs ./dist/setup/setup.hs
 # Should be able to build setup without extra dependencies
- - /opt/ghc/$GHCVER/bin/ghc --make -odir ./dist/setup -hidir ./dist/setup -i -i. ./dist/setup/setup.hs -o ./dist/setup/setup -threaded  # the command cabal-install would use to build setup
+ - /opt/ghc/$GHCVER/bin/ghc --make -odir ./dist/setup -hidir ./dist/setup -i -i. ./dist/setup/setup.hs -o ./dist/setup/setup -Werror -threaded  # the command cabal-install would use to build setup
 
 # Need extra dependencies for test suite
  - cabal install --only-dependencies --enable-tests
  - sudo /opt/ghc/$GHCVER/bin/ghc-pkg recache
  - /opt/ghc/$GHCVER/bin/ghc-pkg recache --user
 
- - ./dist/setup/setup configure --user --enable-tests --enable-benchmarks -v2  # -v2 provides useful information for debugging
+ - ./dist/setup/setup configure --user --enable-tests --enable-benchmarks --ghc-option=-Werror -v2  # -v2 provides useful information for debugging
  - ./dist/setup/setup build   # this builds all libraries and executables (including tests/benchmarks)
  - ./dist/setup/setup haddock # see #2198
  - ./dist/setup/setup test --show-details=streaming
@@ -58,7 +58,7 @@ script:
  - cabal sandbox init
  - cabal sandbox add-source ../Cabal
  - cabal install --dependencies-only --enable-tests
- - cabal configure --enable-tests
+ - cabal configure --enable-tests --ghc-option=-Werror
  - cabal build
  - cabal test
  - cabal check

Cabal/Distribution/PackageDescription/PrettyPrint.hs

@@ -27,8 +27,8 @@ import Distribution.PackageDescription
         Flag(..), PackageDescription(..),
         GenericPackageDescription(..))
 import Text.PrettyPrint
-       (hsep, comma, punctuate, parens, char, nest, empty,
-        isEmpty, ($$), (<+>), colon, (<>), text, vcat, ($+$), Doc, render)
+       (hsep, parens, char, nest, empty, isEmpty, ($$), (<+>),
+        colon, (<>), text, vcat, ($+$), Doc, render)
 import Distribution.Simple.Utils (writeUTF8File)
 import Distribution.ParseUtils (showFreeText, FieldDescr(..), indentWith, ppField, ppFields)
 import Distribution.PackageDescription.Parse (pkgDescrFieldDescrs,binfoFieldDescrs,libFieldDescrs,

Cabal/Distribution/Simple/GHC.hs

@@ -885,6 +885,7 @@ getRPaths lbi clbi | supportRPaths hostOS = do
     supportRPaths IRIX        = False
     supportRPaths HaLVM       = False
     supportRPaths IOS         = False
+    supportRPaths Android     = False
     supportRPaths Ghcjs       = False
     supportRPaths (OtherOS _) = False
     -- Do _not_ add a default case so that we get a warning here when a new OS

Cabal/Distribution/Simple/GHCJS.hs

@@ -76,7 +76,6 @@ import System.Directory         ( doesFileExist )
 import System.FilePath          ( (</>), (<.>), takeExtension,
                                   takeDirectory, replaceExtension,
                                   splitExtension )
-import Distribution.Compat.Exception (catchIO)
 
 configure :: Verbosity -> Maybe FilePath -> Maybe FilePath
           -> ProgramConfiguration

Cabal/Distribution/Simple/PreProcess.hs

@@ -557,6 +557,7 @@ platformDefines lbi =
       IRIX      -> ["irix"]
       HaLVM     -> []
       IOS       -> ["ios"]
+      Android   -> ["android"]
       Ghcjs     -> ["ghcjs"]
       OtherOS _ -> []
     archStr = case hostArch of