ghc-pkg "cache is out of date" message breaks testsuite

Since the merge of the package database locking business, ghc-pkg dump spews a message on stderr on Windows,

$ "C:/msys64/home/ben/ghc/inplace/bin/ghc-pkg.exe" dump
WARNING: cache is out of date: C:\msys64\home\ben\ghc\inplace\lib\package.conf.d\package.cache
ghc will see an old view of this package db. Use 'ghc-pkg recache' to fix.
name: xhtml
version: 3000.2.1
id: xhtml-3000.2.1
...

When the testsuite driver sees this it (namely testutil.getStdout) assumes something has gone terribly wrong and aborts.

From a cursory look it's not clear how we got into this situation; the file indeed exists and was certainly touched during the build. However, running ghc-pkg recache indeed seems to fix the issue.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	highest
Resolution	Unresolved
Component	ghc-pkg
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	arybczak
Operating system
Architecture