fix: display errors when schema validation fails

Author: chronicc

src/molecule/config.py

@@ -751,7 +751,7 @@ def _validate(self) -> None:
 
         errors = schema_v3.validate(self.config)
         if errors:
-            msg = f"Failed to validate {self.molecule_file}\n\n{errors}"
+            msg = f"Failed to validate {self.molecule_file}\n\n{'\n'.join(errors)}"
             sysexit_with_message(msg, code=1)