Make generateSingleHeader.py Python 2.7 compatible

scripts/generateSingleHeader.py

@@ -36,8 +36,11 @@ for arg in sys.argv[1:]:
         print( "\n** Unrecognised argument: " + arg + " **\n" )
         exit(1)
 
-# ensure that the output directory exists
-os.makedirs(os.path.dirname(outputPath), exist_ok = True)
+
+# ensure that the output directory exists (hopefully no races)
+outDir = os.path.dirname(outputPath)
+if not os.path.exists(outDir):
+    os.makedirs(outDir)
 out = open( outputPath, 'w' )
 ifdefs = 0
 implIfDefs = -1