func (s *charmSuite) assertParseCharmTagInvalid(c *gc.C, tag string) {
_, err := names.ParseCharmTag(tag)
c.Check(err, gc.ErrorMatches, fmt.Sprintf(".*%q is not a valid.*", tag))
}
func (s *charmSuite) assertParseCharmTagValid(c *gc.C, tag string, expected names.Tag) {
got, err := names.ParseCharmTag(tag)
c.Assert(err, jc.ErrorIsNil)
c.Check(got, gc.FitsTypeOf, expected)
c.Check(got, gc.Equals, expected)
}