func (c *Client) AssignIssue(org, repo string, number int, logins []string) error {
	c.log("AssignIssue", org, repo, number, logins)
	assigned := make(map[string]bool)
	var i Issue
	_, err := c.request(&request{
		method:      http.MethodPost,
		path:        fmt.Sprintf("/repos/%s/%s/issues/%d/assignees", org, repo, number),
		requestBody: map[string][]string{"assignees": logins},
		exitCodes:   []int{201},
	}, &i)
	if err != nil {
		return err
	}
	for _, assignee := range i.Assignees {
		assigned[NormLogin(assignee.Login)] = true
	}
	missing := MissingUsers{action: "assign"}
	for _, login := range logins {
		if !assigned[NormLogin(login)] {
			missing.Users = append(missing.Users, login)
		}
	}
	if len(missing.Users) > 0 {
		return missing
	}
	return nil
}
func (c *Client) AssignIssue(org, repo string, number int, logins []string) error {
	c.log("AssignIssue", org, repo, number, logins)
	assigned := make(map[string]bool)
	var i Issue
	_, err := c.request(&request{
		method:      http.MethodPost,
		path:        fmt.Sprintf("/repos/%s/%s/issues/%d/assignees", org, repo, number),
		requestBody: map[string][]string{"assignees": logins},
		exitCodes:   []int{201},
	}, &i)
	if err != nil {
		return err
	}
	for _, assignee := range i.Assignees {
		assigned[NormLogin(assignee.Login)] = true
	}
	missing := MissingUsers{action: "assign"}
	for _, login := range logins {
		if !assigned[NormLogin(login)] {
			missing.Users = append(missing.Users, login)
		}
	}
	if len(missing.Users) > 0 {
		return missing
	}
	return nil
}
// AssignIssue adds logins to org/repo#number, returning an error if any login is missing after making the call.
//
// See https://developer.github.com/v3/issues/assignees/#add-assignees-to-an-issue