[GHC] #13354: Package database locking patch broke ghc-pkg with non-existent database

[GHC]

#13354: Package database locking patch broke ghc-pkg with non-existent database
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  highest        |         Milestone:  8.2.1
          Component:  Package        |           Version:  8.0.1
  system                             |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 It seems that Phab:D3090 (#13194) broke `ghc-pkg`'s behavior in the face
 of non-existent package databases. Namely, `cabal install` fails during
 registration with,
 {{{
 Creating package registration file: /tmp/pkgConf-
 compact-0.1.0.1-13684/pkgConf
 ("/opt/exp/ghc/roots/master/bin/ghc-pkg",["update","-","--global","--
 user","-v2"])
 /opt/exp/ghc/roots/master/bin/ghc-pkg returned ExitFailure 1 with error
 message:
 ghc-pkg: Couldn't open database
 /home/ben/.ghc/x86_64-linux-8.1.20170227/package.conf.d for modification:
 /home/ben/.ghc/x86_64-linux-8.1.20170227/package.conf.d.lock:
 openBinaryFile:
 does not exist (No such file or directory)
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13354>
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