title: python-re.sub() and unicode
body: <p>I want to replace all emoji with <code>''</code> but my regEx doesn't work.<BR>For example, </p>
  
  <pre><code>content= u'?\u86cb\u767d12\U0001f633\uff0c\u4f53\u6e29\u65e9\u6668\u6b63\u5e38\uff0c\u5348\u540e\u665a\u95f4\u53d1\u70ed\uff0c\u6211\u73b0\u5728\u8be5\u548b\U0001f633?'
  </code></pre>
  
  <p>and I want to replace all the forms like <code>\U0001f633</code> with <code>''</code> so I write the code:</p>
  
  <p><code>print re.sub(ur'\\U[0-9a-fA-F]{8}','',content)</code><br></p>
  
  <p>But it doesn't work.<br>
  Thanks a lot. </p>