I'm not sure what you mean here... If the statements fail for whatever reason, then something is clearly wrong (e.g. 'source' dir is not there), and then you should fail.

E.g.:

```python
try:
    shutil.copy("build/MakePAR", "source/Makefile")
    os.chdir("source")
except OSError, err:
    self.log.error("Failed to configure DL_POLY_Classes because an error occured: %s" % err)
```

Afaik, an error like this is not handled higher up, so it would just result in a traceback without a clear error message.