allow dirs that don't contain go files

cmd/dep/testdata/harness_tests/ensure/pkg-errors/case1/testcase.json

@@ -3,6 +3,6 @@
     ["init", "-no-examples", "-skip-tools"],
     ["ensure", "-update"]
   ],
-  "error-expected": "no dirs contained any Go code",
+  "error-expected": "",
   "vendor-final": []
 }

cmd/dep/testdata/harness_tests/ensure/pkg-errors/case2/testcase.json

@@ -2,6 +2,6 @@
     "commands": [
         ["ensure"]
     ],
-    "error-expected": "found 1 errors",
+    "error-expected": "",
     "vendor-final": []
 }

gps/pkgtree/pkgtree.go

@@ -221,10 +221,6 @@ func fillPackage(p *build.Package) error {
 		return err
 	}
 
-	if len(gofiles) == 0 {
-		return &build.NoGoError{Dir: p.Dir}
-	}
-
 	var testImports []string
 	var imports []string
 	var importComments []string

gps/pkgtree/pkgtree_test.go

@@ -6,7 +6,6 @@ package pkgtree
 
 import (
 	"fmt"
-	"go/build"
 	"go/scanner"
 	"go/token"
 	"io/ioutil"
@@ -18,6 +17,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/davecgh/go-spew/spew"
 	"github.com/golang/dep/gps/paths"
 	"github.com/golang/dep/internal/fs"
 )
@@ -489,8 +489,9 @@ func TestListPackages(t *testing.T) {
 				ImportRoot: "empty",
 				Packages: map[string]PackageOrErr{
 					"empty": {
-						Err: &build.NoGoError{
-							Dir: j("empty"),
+						P: Package{
+							ImportPath: "empty",
+							Imports:    []string{},
 						},
 					},
 				},
@@ -733,8 +734,9 @@ func TestListPackages(t *testing.T) {
 				ImportRoot: "ren",
 				Packages: map[string]PackageOrErr{
 					"ren": {
-						Err: &build.NoGoError{
-							Dir: j("ren"),
+						P: Package{
+							ImportPath: "ren",
+							Imports:    []string{},
 						},
 					},
 					"ren/m1p": {
@@ -1653,8 +1655,9 @@ func TestListPackagesNoPerms(t *testing.T) {
 		ImportRoot: "ren",
 		Packages: map[string]PackageOrErr{
 			"ren": {
-				Err: &build.NoGoError{
-					Dir: workdir,
+				P: Package{
+					ImportPath: "ren",
+					Imports:    []string{},
 				},
 			},
 			"ren/m1p": {
@@ -1673,6 +1676,8 @@ func TestListPackagesNoPerms(t *testing.T) {
 
 	got, err := ListPackages(workdir, "ren")
 
+	spew.Dump(got)
+
 	if err != nil {
 		t.Fatalf("Unexpected err from ListPackages: %s", err)
 	}
@@ -1690,10 +1695,6 @@ func TestListPackagesNoPerms(t *testing.T) {
 			}
 		}
 
-		if got.Packages["ren"].Err == nil {
-			t.Error("Should have gotten error on empty root directory")
-		}
-
 		if !reflect.DeepEqual(got.Packages["ren/m1p"].P.Imports, want.Packages["ren/m1p"].P.Imports) {
 			t.Error("Mismatch between imports in m1p")
 		}