decouple testfiles from framework

This drops testfiles.ReadOrDie and updated testfiles.Exists to return an
error, forcing the caller to decide whether to call framework.Fail or do
something else.

It makes for a slightly less friendly API, but also means the package is
decoupled from framework again, as per the comments at the top of the
file

test/e2e/framework/testfiles/testfiles.go

@@ -33,8 +33,6 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
-
-	"k8s.io/kubernetes/test/e2e/framework"
 )
 
 var filesources []FileSource
@@ -66,18 +64,6 @@ type FileSource interface {
 	DescribeFiles() string
 }
 
-// ReadOrDie tries to retrieve the desired file content from
-// one of the registered file sources. In contrast to FileSource, it
-// will either return a valid slice or abort the test by calling the fatal function,
-// i.e. the caller doesn't have to implement error checking.
-func ReadOrDie(filePath string) []byte {
-	data, err := Read(filePath)
-	if err != nil {
-		framework.Fail(err.Error(), 1)
-	}
-	return data
-}
-
 // Read tries to retrieve the desired file content from
 // one of the registered file sources.
 func Read(filePath string) ([]byte, error) {
@@ -106,17 +92,17 @@ func Read(filePath string) ([]byte, error) {
 // Exists checks whether a file could be read. Unexpected errors
 // are handled by calling the fail function, which then should
 // abort the current test.
-func Exists(filePath string) bool {
+func Exists(filePath string) (bool, error) {
 	for _, filesource := range filesources {
 		data, err := filesource.ReadTestFile(filePath)
 		if err != nil {
-			framework.Fail(fmt.Sprintf("fatal error looking for test file %s: %s", filePath, err), 1)
+			return false, err
 		}
 		if data != nil {
-			return true
+			return true, nil
 		}
 	}
-	return false
+	return false, nil
 }
 
 // RootFileSource looks for files relative to a root directory.