[Hackage] #550: bad error message when proxy cannot be resolved

[Hackage]

#550: bad error message when proxy cannot be resolved
---------------------------------+------------------------------------------
  Reporter:  duncan              |        Owner:     
      Type:  defect              |       Status:  new
  Priority:  low                 |    Milestone:     
 Component:  cabal-install tool  |      Version:     
  Severity:  minor               |     Keywords:     
Difficulty:  easy (<4 hours)     |   Ghcversion:     
  Platform:                      |  
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 As reported by a user:

 {{{
 when I run cabal update I get some strange error:
 % cabal update
 Downloading the latest package list from hackage.haskell.org
 cabal: user error (openTCPConnection: host lookup failure for "")
 }}}

 Turns out the problem was that `http_proxy` environment variable was set
 to "" (ie the empty string).

 The problem with the error of course is that we've no idea what it is it
 thinks is "", there's no indication that it's the proxy. If it said that
 it encountered the problem while contacting the proxy that'd be an
 improvement.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/550>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects