title: invalid load key, '\x00' issue in Unplicling
body: <p>I'm beginner of Data Analytics.
  I'm trying to convert pickle file to python but i can't solve this problem.</p>
  
  <p>I'm looking this problem at here and google but there is no exact answer....</p>
  
  <p>Could you help me please?</p>
  
  <pre><code>import pickle
  
  with open("xgb_tuning_train_data.pkl", "rb") as fr:
      data = pickle.load(fr)
  
  ---------------------------------------------------------------------------
  UnpicklingError                           Traceback (most recent call last)
  &lt;ipython-input-5-d0e5155fc161&gt; in &lt;module&gt;()
        2 
        3 with open("xgb_tuning_train_data.pkl", "rb") as fr:
  ----&gt; 4     data = pickle.load(fr)
  
  UnpicklingError: invalid load key, '\x00'.
  </code></pre>