isolate: give up and die on file unavailability

client/isolate/isolate.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package isolate
 
 import (
         "bytes"
         "encoding/json"
         "errors"
@@ skipping 261 matching lines @@
                 } else {
                         // Grab the stats right away.
                         info, err := os.Lstat(dep)
                         if err != nil {
                                 return nil, err
                         }
                         mode := info.Mode()
                         if mode&os.ModeSymlink == os.ModeSymlink {
                                 l, err := os.Readlink(dep)
                                 if err != nil {
-                                        return nil, err
+                                        // Kill the process: there's no reason to continue if a file is
+                                        // unavailable.
+                                        log.Fatalf("Unable to stat %q: %v", dep, err)
                                 }
                                 i.Files[relPath] = isolated.SymLink(l)
                         } else {
                                 i.Files[relPath] = isolated.BasicFile("", int(mode.Perm()), info.Size())
                                 fileItems = append(fileItems, arch.PushFile(relPath, dep, -info.Size()))
                         }
                 }
         }
 
         for _, item := range fileItems {
@@ skipping 24 matching lines @@
         raw := &bytes.Buffer{}
         if err = json.NewEncoder(raw).Encode(i); err != nil {
                 return nil, err
         }
 
         if err := ioutil.WriteFile(opts.Isolated, raw.Bytes(), 0644); err != nil {
                 return nil, err
         }
         return arch.Push(displayName, isolatedclient.NewBytesSource(raw.Bytes()), 0), nil
 }