issue.go
func NewIssue(linter string, formatTmpl *template.Template) (*Issue, error) {
	issue := &Issue{
		Line:       1,
		Severity:   Warning,
		Linter:     linter,
		formatTmpl: formatTmpl,
	}
	err := formatTmpl.Execute(ioutil.Discard, issue)
	return issue, err
}
func NewIssue(linter string, formatTmpl *template.Template) (*Issue, error) {
	issue := &Issue{
		Line:       1,
		Severity:   Warning,
		Linter:     linter,
		formatTmpl: formatTmpl,
	}
	err := formatTmpl.Execute(ioutil.Discard, issue)
	return issue, err
}
// NewIssue returns a new issue. Returns an error if formatTmpl is not a valid
// template for an Issue.