Python 3.5 compatibility

Author: konstin

setuptools_rust/build.py

@@ -71,7 +71,8 @@ def build_extension(self, ext):
 
         # Find where to put the temporary build files created by `cargo`
         metadata_command = ["cargo", "metadata", "--manifest-path", ext.path, "--format-version", "1"]
-        metadata = json.loads(check_output(metadata_command))
+        # The decoding is needed for python 3.5 compatibility
+        metadata = json.loads(check_output(metadata_command).decode())
         target_dir = metadata["target_directory"]
 
         if not os.path.exists(ext.path):