on`` is not safe enough
>>> parse_version(_forgiving_version('0.23ubuntu1'))
<Version('0.23.dev0+sanitized.ubuntu1')>
>>> parse_version(_forgiving_version('0.23-'))
<Version('0.23.dev0+sanitized')>
>>> parse_version(_forgiving_version('0.-_'))
<Version('0.dev0+sanitized')>
>>> parse_version(_forgiving_version('42.+?1'))
<Version('42.dev0+sanitized.1')>
>>> parse_version(_forgiving_version('hello world'))
<Version('0.dev0+sanitized.hello.world')>
r4