Make ContinueOnError actually work

In resource.Builder ContinueOnError() should actually do so.

Reorganized util.CheckErr() to make it display bulk errors more
effectively and be more reusable. Clarified that CheckErr is not
specific to kubectl in Godoc. Changed the "Error: " prefix to
"error: " to more closely match Unix conventions.

pkg/kubectl/resource/builder_test.go

@@ -18,6 +18,7 @@ package resource
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"net/http"
@@ -606,6 +607,36 @@ func TestMultipleObject(t *testing.T) {
 	}
 }
 
+func TestContinueOnErrorVisitor(t *testing.T) {
+	r, _, _ := streamTestData()
+	req := NewBuilder(latest.RESTMapper, api.Scheme, fakeClient()).
+		ContinueOnError().
+		NamespaceParam("test").Stream(r, "STDIN").Flatten().
+		Do()
+	count := 0
+	testErr := fmt.Errorf("test error")
+	err := req.Visit(func(_ *Info) error {
+		count++
+		if count > 1 {
+			return testErr
+		}
+		return nil
+	})
+	if err == nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if count != 3 {
+		t.Fatalf("did not visit all infos: %d", count)
+	}
+	agg, ok := err.(errors.Aggregate)
+	if !ok {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(agg.Errors()) != 2 || agg.Errors()[0] != testErr || agg.Errors()[1] != testErr {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 func TestSingularObject(t *testing.T) {
 	obj, err := NewBuilder(latest.RESTMapper, api.Scheme, fakeClient()).
 		NamespaceParam("test").DefaultNamespace().