Fix for read only files

Author: aaronbog

src/pythainer/builders/cmds.py

@@ -105,6 +105,7 @@ def get_str_for_dockerfile(
         if os.path.isfile(self._source_path):
             shutil.copyfile(self._source_path, docker_file_Path / self._source_path)
         elif os.path.isdir(self._source_path):
+            shutil.rmtree(docker_file_Path / self._source_path)
             shutil.copytree(self._source_path, docker_file_Path / self._source_path,dirs_exist_ok=True)
         else:
             raise FileExistsError(f'{self._source_path} is not a valid target to copy into the docker container')