def extraction_error(self):
        """Give an error message for problems extracting file(s)"""

        old_exc = sys.exc_info()[1]
        cache_path = self.extraction_path or get_default_cache()

        err = ExtractionError("""Can't extract file(s) to egg cache

The following error occurred while trying to extract file(s) to the Python egg
cache:

  %s

The Python egg cache directory is currently set to:

  %s

Perhaps your account does not have write access to this directory?  You can
change the cache directory by setting the PYTHON_EGG_CACHE environment
variable to point to an accessible directory.
""" % (old_exc, cache_path)
        )
        err.manager = self
        err.cache_path = cache_path
        err.original_error = old_exc
        raise err
Give an error message for problems extracting file(s)