Adds integration test for commercialhaskell#3396

The provided test package (dinamo), that is part of a custom snapshot has
a malformed cabal file. Specifically, it's setting the required cabal
version to an invalid number (9001). This test makes sure that
stack does not care about this if we do not actually use the package
in our project.

test/integration/IntegrationSpec.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE DeriveDataTypeable  #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 
 import           Control.Applicative
@@ -15,14 +15,14 @@ import           Data.Conduit.Binary          (sinkLbs)
 import           Data.Conduit.Filesystem      (sourceDirectoryDeep)
 import qualified Data.Conduit.List            as CL
 import           Data.Conduit.Process
-import           Data.List                    (isSuffixOf, stripPrefix, sort)
+import           Data.List                    (isSuffixOf, sort, stripPrefix)
 import qualified Data.Map                     as Map
 import           Data.Maybe                   (fromMaybe)
 import           Data.Text.Encoding.Error     (lenientDecode)
 import qualified Data.Text.Lazy               as TL
 import qualified Data.Text.Lazy.Encoding      as TL
 import           Data.Typeable
-import           Prelude -- Fix redundant import warnings
+import           Prelude
 import           System.Directory
 import           System.Environment
 import           System.Exit
@@ -38,7 +38,7 @@ main = do
     let findExe name = do
             mexe <- findExecutable name
             case mexe of
-                Nothing -> error $ name ++ " not found on PATH"
+                Nothing  -> error $ name ++ " not found on PATH"
                 Just exe -> return exe
     runghc <- findExe "runghc"
     stack <- findExe "stack"
@@ -136,7 +136,7 @@ toCopyRoot srcfp = any (`isSuffixOf` srcfp)
     -- copied, trade-off of runtime/bandwidth vs isolation of tests
     [ ".tar"
     , ".xz"
-    -- , ".gz"
+    , ".gz"
     , ".7z.exe"
     , "00-index.cache"
     ]

test/integration/tests/3396-package-indices/Main.hs

@@ -0,0 +1,4 @@
+import           StackTest
+
+main :: IO ()
+main = stack ["build"]

test/integration/tests/3396-package-indices/files/files.cabal

@@ -0,0 +1,19 @@
+name:                files
+version:             0.1.0.0
+-- synopsis:
+-- description:
+homepage:            https://github.com/githubuser/files#readme
+license:             BSD3
+author:              Author name here
+maintainer:          example@example.com
+copyright:           2017 Author name here
+category:            Web
+build-type:          Simple
+cabal-version:       >=1.10
+
+library
+  hs-source-dirs:      src
+  exposed-modules:     Lib
+  build-depends:       base >= 4.7 && < 5
+  default-language:    Haskell2010
+

test/integration/tests/3396-package-indices/files/my-snapshot.yaml

@@ -0,0 +1,11 @@
+compiler: ghc-8.0.2
+name: my-snapshot
+
+packages:
+  - base-4.10.0.0
+  - dinamo-0.1.0.0
+
+flags:
+  dinamo:
+    debug: true
+

test/integration/tests/3396-package-indices/files/src/Lib.hs

@@ -0,0 +1,8 @@
+module Lib
+    ( someFunc
+    ) where
+
+
+someFunc :: IO ()
+someFunc = print "some func"
+

test/integration/tests/3396-package-indices/files/stack.yaml

@@ -0,0 +1,18 @@
+resolver: my-snapshot.yaml
+
+packages:
+- .
+
+extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+flags: {}
+
+# Extra package databases containing global packages
+extra-package-dbs: []
+
+package-indices:
+  - name: CustomIndex
+    download-prefix: http://0.0.0.0:8080/
+    http: http://0.0.0.0:8080/custom.index.tar.gz
+