title: cabal sandbox install still fails with "packages are likely to be broken by the reinstalls"
body: <p>I'm trying to build the <a href="http://elm-lang.org/" rel="noreferrer">Elm Platform</a> using a cabal sandbox. The installation fails however with the message "packages are likely to be broken by the reinstalls". This seems to me to contradict the whole purpose of sandboxing, which I had believed was supposed to avoid this kind of error.</p>
  
  <p>Can anybody explain this error for me, and even better help me proceed with the Elm install? Is it safe to add <code>--force-reinstalls</code>?</p>
  
  <p>Here are the sequence of commands I executed:</p>
  
  <pre><code>cabal sandbox init
  cabal update
  cabal install -j elm-compiler-0.14 elm-package-0.2 elm-make-0.1 elm-reactor-0.2 elm-repl-0.4
  </code></pre>
  
  <p>I'm using cabal 1.22.0.0 and GHC 7.8.2 on Mac OS 10.10. The full output as follows:</p>
  
  <pre><code>Resolving dependencies...
  In order, the following would be installed:
  Diff-0.3.0 (new package)
  HUnit-1.2.5.2 (new package)
  ansi-terminal-0.6.2.1 (new package)
  ansi-wl-pprint-0.6.7.1 (new package)
  async-2.0.2 (new package)
  blaze-markup-0.6.2.0 (new package)
  blaze-html-0.7.0.3 (new package)
  byteable-0.1.1 (new package)
  bytestring-mmap-0.2.2 (new package)
  bytestring-trie-0.2.4 (new package)
  cereal-0.4.1.1 (new package)
  cmdargs-0.10.12 (new package)
  concatenative-1.0.1 (new package)
  cookie-0.4.1.4 (new package)
  cryptohash-0.11.6 (new package)
  enumerator-0.4.20 (new package)
  attoparsec-enumerator-0.3.3 (new package)
  blaze-builder-enumerator-0.2.0.6 (new package)
  exceptions-0.6.1 (reinstall) changes: mtl-2.1.3.1 -&gt; 2.2.1,
  transformers-0.3.0.0 -&gt; 0.4.1.0
  extensible-exceptions-0.1.1.4 (new package)
  hfsevents-0.1.5 (new package)
  fsnotify-0.1.0.3 (new package)
  hourglass-0.2.8 (new package)
  asn1-types-0.3.0 (new package)
  asn1-encoding-0.9.0 (new package)
  asn1-parse-0.9.0 (new package)
  crypto-pubkey-types-0.4.2.3 (new package)
  http-types-0.8.5 (new package)
  mime-types-0.1.0.5 (new package)
  monads-tf-0.1.0.2 (reinstall) changes: transformers-0.3.0.0 -&gt; 0.4.1.0
  MonadCatchIO-transformers-0.3.1.3 (new package)
  network-2.6.0.2 (new version)
  parsec-3.1.7 (new version)
  indents-0.3.3 (new package)
  network-uri-2.6.0.1 (new package)
  HTTP-4000.2.19 (new version)
  pem-0.2.2 (new package)
  prettyclass-1.0.0.0 (new package)
  language-glsl-0.1.1 (new package)
  publicsuffixlist-0.1 (new package)
  regex-base-0.93.2 (new package)
  regex-posix-0.95.2 (new package)
  securemem-0.1.4 (new package)
  crypto-cipher-types-0.0.9 (new package)
  cipher-aes-0.2.9 (new package)
  cipher-des-0.0.6 (new package)
  cipher-rc4-0.1.4 (new package)
  crypto-random-0.0.8 (new package)
  cprng-aes-0.6.1 (new package)
  crypto-numbers-0.2.7 (new package)
  crypto-pubkey-0.2.7 (new package)
  socks-0.5.4 (new package)
  streaming-commons-0.1.8 (new package)
  http-client-0.3.8.2 (latest: 0.4.6.2) (new package)
  syb-0.4.4 (new package)
  tagshare-0.0 (new package)
  terminfo-0.4.0.0 (new package)
  haskeline-0.7.1.3 (new package)
  tf-random-0.5 (new package)
  QuickCheck-2.7.6 (new package)
  testing-feat-0.4.0.2 (new package)
  transformers-compat-0.3.3.4 (new package)
  optparse-applicative-0.10.0 (latest: 0.11.0.1) (new package)
  union-find-0.2 (new package)
  unix-compat-0.4.1.4 (new package)
  unordered-containers-0.2.5.1 (new package)
  aeson-0.8.0.2 +old-locale (new package)
  aeson-pretty-0.7.2 (new package)
  uniplate-1.6.12 (new package)
  websockets-0.9.2.2 (new version)
  wl-pprint-1.1 (new package)
  language-ecmascript-0.16.2 (latest: 0.17) (new package)
  elm-compiler-0.14 (new package)
  x509-1.5.0.1 (new package)
  x509-store-1.5.0 (new package)
  x509-system-1.5.0 (new package)
  x509-validation-1.5.1 (new package)
  tls-1.2.13 (new package)
  connection-0.2.3 (new package)
  http-client-tls-0.2.2 (new package)
  zip-archive-0.2.3.5 (new version)
  elm-package-0.2 (latest: 0.2.2) (new package)
  elm-make-0.1 (new package)
  elm-repl-0.4 (new package)
  zlib-enum-0.2.3.1 (new package)
  snap-core-0.9.6.4 (new package)
  snap-server-0.9.4.6 (new package)
  websockets-snap-0.9.0.0 (new package)
  elm-reactor-0.2 (latest: 0.2.0.1) (new package)
  cabal: The following packages are likely to be broken by the reinstalls:
  temporary-1.2.0.3
  shellmate-0.1.6
  Use --force-reinstalls if you want to install anyway.
  </code></pre>
  
  <p>UPDATE:</p>
  
  <p>As requested, the output from <code>cabal exec ghc-pkg list temporary</code>:</p>
  
  <pre><code>$ cabal exec ghc-pkg list temporary
  /Applications/ghc-7.8.2.app/Contents/lib/ghc-7.8.2/package.conf.d
     temporary-1.2.0.3
  /Users/nbartlett/Development/Elm-Platform/tmp/.cabal-sandbox/x86_64-osx-ghc-7.8.2-packages.conf.d
  </code></pre>