Adapt tests to a change in TFile "file not found" error message

A recent PR in ROOT master changed the way TFile file not found errors are reported.

This MR modifies the affected tests to absorb the difference.

/cc @mato @sailer @ganis

GaudiExamples/tests/qmtest/gaudiexamples.qms/jira.qms/gaudi_971.qmt

@@ -51,6 +51,14 @@ FileCatalog(Catalogs = [ "xmlcatalog_file:GAUDI-971.xml" ])
 esel = EventSelector()
 esel.Input = ["DATAFILE='LFN:input.dst'  SVC='Gaudi::RootEvtSelector' OPT='READ'"]
 
+</text></argument>
+<argument name="validator"><text>
+preprocessor = normalizeExamples + \
+    RegexpReplacer(when = "TFile::TFile",
+        orig = r"file (.*)dummy.dst does not exist",
+        repl = r"file .../dummy.dst does not exist")
+
+validateWithReference(preproc = preprocessor)
 </text></argument>
 <argument name="reference"><text>refs/jira/gaudi_971.ref</text></argument>
 <argument name="error_reference"><text>refs/jira/gaudi_971.err.ref</text></argument>