[Hackage] #671: better error message for broken build tools

[Hackage]

#671: better error message for broken build tools
------------------------------+---------------------------------------------
  Reporter:  duncan           |        Owner:         
      Type:  defect           |       Status:  new    
  Priority:  normal           |    Milestone:         
 Component:  Cabal library    |      Version:  1.8.0.4
  Severity:  normal           |     Keywords:         
Difficulty:  easy (<4 hours)  |   Ghcversion:         
  Platform:                   |  
------------------------------+---------------------------------------------
 Consider:
 {{{
 Configuring haskell-src-exts-1.9.0...
 setup: happy version >=1.17 is required but the version of
 /usr/local/bin/happy could not be determined.
 }}}

 The actual problem is:
 {{{
 /usr/local/bin/happy: error while loading shared libraries: libgmp.so.3:
 cannot open shared object file: No such file or directory
 }}}

 We could produce a better error message in this situation. If we get a
 non-0 exit code when we check the `--version` then we can probably safely
 report that the program is probably broken. Of course if we get some
 result text back and we cannot extract and parse the version number then
 that's different.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/671>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects