Fix detection of platform specific reference files

Closes #236

See merge request !1398

GaudiPolicy/python/GaudiTesting/BaseTest.py

@@ -681,11 +681,9 @@ class BaseTest(object):
             return ""
 
         # function to split an extension in constituents parts
-        def platformSplit(p):
-            import re
+        import re
 
-            delim = re.compile("-" in p and r"[-+]" or r"_")
-            return set(delim.split(p))
+        platformSplit = lambda p: set(re.split(r"[-+]", p))
 
         reference = os.path.normpath(
             os.path.join(self.basedir, os.path.expandvars(reffile))