message: where i got execute from
diff: @@ -79,6 +79,6 @@ def regression_test(threshold):
  f = open("test.sh", "w")
  f.write(exp)
  f.close()
  - os.execute("chmod +x test.sh")
  + os.system("chmod +x test.sh")
  regression_test(0.1)
  \ No newline at end of file
  