Read the configuration parameters from the Yaml file filename.

def from_file(cls, filename):
        """Read the configuration parameters from the Yaml file filename."""
        try:
            with open(filename, "r") as fh:
                return cls.from_dict(yaml.safe_load(fh))
        except Exception as exc:
            print("Error while reading TaskManager parameters from %s\n" % filename)
            raise