def __init__(self, url, **kw):
super(SourcePackage, self).__init__(url, **kw)
ext = Archiver.get_extension(self.filename)
if ext is None:
raise self.InvalidPackage('%s is not a recognized archive format.' % self.filename)
fragment = self.filename[:-len(ext)]
self._name, self._raw_version = self.split_fragment(fragment)
