cmd: No longer panic if cwd is deleted

cmd/plugins/juju-metadata/metadata.go

 // Copyright 2012, 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package main
 
 import (
         "fmt"
         "os"
 
         "github.com/juju/loggo"
 
         "launchpad.net/juju-core/cmd"
         "launchpad.net/juju-core/juju"
         _ "launchpad.net/juju-core/provider/all"
 )
 
 var logger = loggo.GetLogger("juju.plugins.metadata")
 
 var metadataDoc = `
 Juju metadata is used to find the correct image and tools when bootstrapping a
 Juju environment.
 `
 
 // Main registers subcommands for the juju-metadata executable, and hands over control
 // to the cmd package. This function is not redundant with main, because it
 // provides an entry point for testing with arbitrary command line arguments.
 func Main(args []string) {
+        ctx, err := cmd.DefaultContext()
+        if err != nil {
+                fmt.Fprintf(os.Stderr, "error: %v\n", err)
+                os.Exit(2)
+        }
         if err := juju.InitJujuHome(); err != nil {
                 fmt.Fprintf(os.Stderr, "error: %s\n", err)
                 os.Exit(2)
         }
         metadatacmd := cmd.NewSuperCommand(cmd.SuperCommandParams{
                 Name:        "metadata",
                 UsagePrefix: "juju",
                 Doc:         metadataDoc,
                 Purpose:     "tools for generating and validating image and tools metadata",
                 Log:         &cmd.Log{}})
 
         metadatacmd.Register(&ValidateImageMetadataCommand{})
         metadatacmd.Register(&ImageMetadataCommand{})
         metadatacmd.Register(&ToolsMetadataCommand{})
         metadatacmd.Register(&ValidateToolsMetadataCommand{})
         metadatacmd.Register(&SignMetadataCommand{})
 
-        os.Exit(cmd.Main(metadatacmd, cmd.DefaultContext(), args[1:]))
+        os.Exit(cmd.Main(metadatacmd, ctx, args[1:]))
 }
 
 func main() {
         Main(os.Args)
 }