[FIX]error string should not be capitalized

Signed-off-by: Scaat Feng <scaat.feng@gmail.com>

pkg/downloader/manager.go

@@ -273,21 +273,21 @@ func (m *Manager) downloadAll(deps []*chart.Dependency) error {
 			chartPath := filepath.Join(tmpPath, dep.Name)
 			ch, err := loader.LoadDir(chartPath)
 			if err != nil {
-				return fmt.Errorf("Unable to load chart: %v", err)
+				return fmt.Errorf("unable to load chart: %v", err)
 			}
 
 			constraint, err := semver.NewConstraint(dep.Version)
 			if err != nil {
-				return fmt.Errorf("Dependency %s has an invalid version/constraint format: %s", dep.Name, err)
+				return fmt.Errorf("dependency %s has an invalid version/constraint format: %s", dep.Name, err)
 			}
 
 			v, err := semver.NewVersion(ch.Metadata.Version)
 			if err != nil {
-				return fmt.Errorf("Invalid version %s for dependency %s: %s", dep.Version, dep.Name, err)
+				return fmt.Errorf("invalid version %s for dependency %s: %s", dep.Version, dep.Name, err)
 			}
 
 			if !constraint.Check(v) {
-				saveError = fmt.Errorf("Dependency %s at version %s does not satisfy the constraint %s", dep.Name, ch.Metadata.Version, dep.Version)
+				saveError = fmt.Errorf("dependency %s at version %s does not satisfy the constraint %s", dep.Name, ch.Metadata.Version, dep.Version)
 				break
 			}
 			continue