Sublime Text 3 Xml Prettifier Plugin. Created by André Bergonse http://www.bergspot.com/blog/2012/05/formatting-xml-in-sublime-text-2-xmllint/

tidy_xml_lint.py

import sublime, sublime_plugin, subprocess
 
class TidyXmlLintCommand(sublime_plugin.TextCommand):
  def run(self, edit):
    command = "XMLLINT_INDENT='\t' xmllint --format --encode utf-8 -"
 
    # help from http://www.sublimetext.com/forum/viewtopic.php?f=2&p=12451
    if self.view.sel()[0].empty():
      xmlRegion = sublime.Region(0, self.view.size())
    else:
      xmlRegion = self.view.sel()[0]

    p = subprocess.Popen(command, bufsize=-1, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, shell=True)
    result, err = p.communicate(self.view.substr(xmlRegion).encode('utf-8'))

    if err != b"":
      self.view.set_status('xmllint', "xmllint: " + err.decode("utf-8"))
      sublime.set_timeout(self.clear,10000)
    else:
      self.view.replace(edit, xmlRegion, result.decode('utf-8'))
      sublime.set_timeout(self.clear,0)
 
  def clear(self):
    self.view.erase_status('xmllint')

Corrected error reporting