intermittent 'unexpected' results of test ghcpkg01
I get this unexpected error from ghcpkg01
Actual stderr output differs from expected: ... +WARNING: cache is out of date: localXXX/package.cache + use 'ghc-pkg recache' to fix.
when running the full suite, but cannot reproduce it when running just that test; it passes when run individually.
(This was also reported in #5503 (closed).)