conform error strings with staticcheck

Author: abhijeetviswa

constraint.go

@@ -178,7 +178,7 @@ func (c *Constraint) String() string {
 func parseSingle(v string) (*Constraint, error) {
 	matches := constraintRegexp.FindStringSubmatch(v)
 	if matches == nil {
-		return nil, fmt.Errorf("Malformed constraint: %s", v)
+		return nil, fmt.Errorf("malformed constraint: %s", v)
 	}
 
 	check, err := NewVersion(matches[2])

version.go

@@ -63,15 +63,15 @@ func NewSemver(v string) (*Version, error) {
 func newVersion(v string, pattern *regexp.Regexp) (*Version, error) {
 	matches := pattern.FindStringSubmatch(v)
 	if matches == nil {
-		return nil, fmt.Errorf("Malformed version: %s", v)
+		return nil, fmt.Errorf("malformed version: %s", v)
 	}
 	segmentsStr := strings.Split(matches[1], ".")
 	segments := make([]int64, len(segmentsStr))
 	for i, str := range segmentsStr {
 		val, err := strconv.ParseInt(str, 10, 64)
 		if err != nil {
 			return nil, fmt.Errorf(
-				"Error parsing version: %s", err)
+				"error parsing version: %s", err)
 		}
 
 		segments[i] = val