preprocess_frozen_modules.py: make compatible with Python 3.4.

1 files changed, 3 insertions, 1 deletions

diff --git a/tools/preprocess_frozen_modules.py b/tools/preprocess_frozen_modules.py
index e29b54b16..b425ffa2d 100755
--- a/tools/preprocess_frozen_modules.py
+++ b/tools/preprocess_frozen_modules.py
@@ -45,7 +45,9 @@ def copy_and_process(in_dir, out_dir):
             output_file_path = Path(out_dir, input_file_path.relative_to(in_dir))
 
             if file.endswith(".py"):
-                output_file_path.parent.mkdir(parents=True, exist_ok=True)
+                # mkdir() takes an exists_ok=True, but not until Python 3.5.
+                if not output_file_path.parent.exists():
+                    output_file_path.parent.mkdir(parents=True)
                 with input_file_path.open("r") as input, output_file_path.open("w") as output:
                     for line in input:
                         if line.startswith("__version__"):