Use runas to do the install when got EACESS error.

src/command-installer.coffee

@@ -3,6 +3,7 @@ _ = require 'underscore-plus'
 async = require 'async'
 fs = require 'fs-plus'
 mkdirp = require 'mkdirp'
+runas = require 'runas'
 
 symlinkCommand = (sourcePath, destinationPath, callback) ->
   mkdirp path.dirname(destinationPath), (error) ->
@@ -15,6 +16,10 @@ symlinkCommand = (sourcePath, destinationPath, callback) ->
         else
           fs.chmod(destinationPath, 0o755, callback)
 
+symlinkCommandWithPrivilegeSync = (sourcePath, destinationPath) ->
+  runas('/bin/mkdir', ['-p', path.dirname(destinationPath)], admin: true)
+  runas('/bin/ln', ['-s', sourcePath, destinationPath], admin: true) is 0
+
 unlinkCommand = (destinationPath, callback) ->
   fs.unlink destinationPath, (error) ->
     if error? and error.code isnt 'ENOENT'
@@ -22,6 +27,9 @@ unlinkCommand = (destinationPath, callback) ->
     else
       callback()
 
+unlinkCommandWithPrivilegeSync = (destinationPath) ->
+  runas('/bin/rm', ['-f', destinationPath], admin: true) is 0
+
 module.exports =
   getInstallDirectory: ->
     "/usr/local/bin"
@@ -34,11 +42,19 @@ module.exports =
     if fs.existsSync(directory)
       destinationPath = path.join(directory, commandName)
       unlinkCommand destinationPath, (error) =>
+        # Retry with privilige escalation.
+        if error?.code is 'EACCES' and unlinkCommandWithPrivilegeSync(destinationPath)
+          error = null
+
         if error?
           error = new Error "Could not remove file at #{destinationPath}." if error
           callback?(error)
         else
           symlinkCommand commandPath, destinationPath, (error) =>
+            # Retry with privilige escalation.
+            if error?.code is 'EACCES' and symlinkCommandWithPrivilegeSync(commandPath, destinationPath)
+              error = null
+
             error = new Error "Failed to symlink #{commandPath} to #{destinationPath}." if error
             callback?(error)
     else