return string instead of directly printing

Signed-off-by: Zen <[email protected]>

Author: desultory

src/ugrd/initramfs_generator.py

@@ -231,5 +231,5 @@ def run_tests(self) -> None:
             self.logger.debug("No tests executed.")
 
     def __str__(self) -> str:
-        return print(self.config_dict)
+        return str(self.config_dict)