title: pip can not install requirements after docker-compose up
body: <p>i got these errors and warnings after step 6 of sudo docker-compose up</p>
  
  <blockquote>
    <p>WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/asn1crypto/</p>
    
    <p>WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/asn1crypto/</p>
    
    <p>WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/asn1crypto/</p>
    
    <p>‌ WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/asn1crypto/</p>
    
    <p>WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution')': /simple/asn1crypto/</p>
    
    <p>ERROR: Could not find a version that satisfies the requirement asn1crypto==0.24.0 (from -r requirements.txt (line 1)) (from versions: none)</p>
    
    <p>ERROR: No matching distribution found for asn1crypto==0.24.0 (from -r requirements.txt (line 1))</p>
  </blockquote>
  
  <p>this is my Dockerfile codes: </p>
  
  <pre><code>FROM python:3
  ENV PYTHONUNBUFFERED 1
  RUN mkdir /todo_service
  WORKDIR /todo_service
  COPY /requirements.txt /todo_service
  RUN pip install -r requirements.txt
  COPY . /todo_service/
  </code></pre>
  
  <p>what should i do to up it without any warning and err?</p>