Rename variable error to err

`error` is the keywork in golang

Signed-off-by: Dave Chen <dave.chen@arm.com>

test/e2e/framework/testfiles/testfiles.go

@@ -81,12 +81,12 @@ func Read(filePath string) ([]byte, error) {
 	}
 	// Here we try to generate an error that points test authors
 	// or users in the right direction for resolving the problem.
-	error := fmt.Sprintf("Test file %q was not found.\n", filePath)
+	err := fmt.Sprintf("Test file %q was not found.\n", filePath)
 	for _, filesource := range filesources {
-		error += filesource.DescribeFiles()
-		error += "\n"
+		err += filesource.DescribeFiles()
+		err += "\n"
 	}
-	return nil, errors.New(error)
+	return nil, errors.New(err)
 }
 
 // Exists checks whether a file could be read. Unexpected errors