Testcases: allow overriding python version
diff --git a/tests/SConstruct b/tests/SConstruct
index c1b0a75..2f67061 100644
--- a/tests/SConstruct
+++ b/tests/SConstruct
@@ -59,6 +59,7 @@
 if 'PROTOCFLAGS' in ARGUMENTS: env.Replace(PROTOCFLAGS = ARGUMENTS['PROTOCFLAGS'])
 if 'NODEFARGS' in ARGUMENTS: env.Replace(NODEFARGS = ARGUMENTS['NODEFARGS'])
 if 'NOVALGRIND' in ARGUMENTS: env.Replace(NOVALGRIND = ARGUMENTS['NOVALGRIND'])
+if 'PYTHON' in ARGUMENTS: env.Replace(PYTHON = ARGUMENTS['PYTHON'])
 
 # Add the builders defined in site_init.py
 add_nanopb_builders(env)