Minor fix

pystencils/cpu/cpujit.py

@@ -602,7 +602,7 @@ def compile_module(code, code_hash, base_dir, compile_flags=None):
 
     if not os.path.exists(object_file):
         try:
-            with open(src_file, 'xw') as f:
+            with open(src_file, 'x') as f:
                 code.write_to_file(f)
         except FileExistsError:
             pass