Compute JAR id.

        Returns sha1 hash of a given JAR file.

def get_jar_id(jar_path):
        """Compute JAR id.

        Returns sha1 hash of a given JAR file.
        """
        jar_id = ""
        try:
            with open(jar_path, mode="rb") as f:
                m = hashlib.sha1()
                for buf in iter(partial(f.read, 4096), b''):
                    m.update(buf)
            jar_id = m.hexdigest()
        except IOError:
            pass
        return jar_id