[GHC] #10164: Cleanup test framework string formatting

[GHC]

#10164: Cleanup test framework string formatting
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        Reporter:  thomie            |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Test Suite        |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by thomie):

 In 9987c66d7c3a1186acb5a32e92cd6846d71987a5/ghc:
 {{{
 commit 9987c66d7c3a1186acb5a32e92cd6846d71987a5
 Author: Thomas Miedema <thomasmiedema at gmail.com>
 Date:   Tue Mar 17 12:08:59 2015 +0100

     Fix Windows testsuite driver

     This got broken in commit 5258566.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10164#comment:4>
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