title: Pickle file is not recognized in docker
body: <p>I have a python3 application with a few pickle files as an input. The application works, but can't read the pickle files. I checked the pickle files are copied to the container.
  Reading CSV files seems ok.</p>
  
  <p>I tried to create a new test pickle file inside the container but didn't work.</p>
  
  <p>Dockerfile</p>
  
  <pre><code>FROM python:3
  
  COPY requirements.txt ./
  RUN pip install --no-cache-dir -r requirements.txt
  
  COPY . .
  
  CMD [ "python", "app/main.py" ]
  
  </code></pre>
  
  <p>Logs</p>
  
  <pre><code>generating values, it will take some time...
  start simulation
  step 1, time spent: 0.38000479599998016
  step 2, time spent: 0.4123095479999961
  step 3, time spent: 0.4407059019999906
  step 4, time spent: 0.43041304799999125
  step 5, time spent: 0.4444566669999972
  step 6, time spent: 0.45184545699999035
  step 7, time spent: 0.4395601109999916
  step 8, time spent: 0.462191746999963
  step 9, time spent: 0.47820707500000026
  step 10, time spent: 0.44471388899995645
  data stored
  
  </code></pre>
  
  <p>At generating values, it should read pickle files already there but didn't.</p>
  
  <p>Any suggestion on how to solve this?</p>
  
  <p>Thanks </p>