title: ValueError: Location based indexing can only have [labels (MUST BE IN THE INDEX)
body: <p>I'm trying to remove duplicates from one dataframe from other with this:</p>
  
  <pre><code>frame = frame.loc[frame.index.difference(properties.index), ]
  </code></pre>
  
  <p>But I`m receiving this error:</p>
  
  <pre><code>ValueError: Location based indexing can only have [labels (MUST BE IN THE INDEX), slices of labels (BOTH endpoints included! Can be slices of integers if the index is integers), listlike of labels, boolean] types
  </code></pre>
  
  <p>This is frame.index:</p>
  
  <pre><code>&gt;&gt;&gt; frame.index
  Index([ u'(11) 4451-5818', u'(11) 96949-2162',  u'(11) 5536-5052',
          u'(11) 5084-1481',  u'(11) 3846-6720',  u'(11) 3067-4424',
          u'(11) 3256-5330',  u'(11) 5181-4004',  u'(11) 3078-0760',
          u'(11) 3152-6111',
         ...
          u'(11) 2541-7538',  u'(11) 2057-7777',  u'(11) 3283-0473',
          u'(11) 2231-3614',  u'(11) 5615-6101',  u'(11) 2242-4927',
          u'(11) 2849-7040',  u'(11) 2456-4342',  u'(11) 2541-0284',
          u'(11) 3051-5881'],
        dtype='object', name=u'phone', length=18039)
  
  &gt;&gt;&gt; properties.index
  Index([u'(01) 13562-7550', u'(11) 5051-1959', u'(11) 3052-1878',
         u'(11) 3849-5839', u'(11) 3203-0996', u'(11) 3258-2578',
         u'(11) 3051-4545', u'(11) 5542-1680', u'(11) 3159-8889',
         u'(11) 3283-2349',
         ...
         u'(11) 2305-2200', u'(18) 997389999', u'(11) 3868-4884',
         u'(11) 3259-0932', u'(11) 3081-2158', u'(11) 3034-6500',
         u'(11) 5082-4308', u'(11) 34346467', u'', u'(11) 31923858'],
        dtype='object', name=u'phone', length=1279)
  </code></pre>
  
  <p>How can I fix this?</p>