解决使用Dockerfile来build镜像时pip install遇到的BUG

错误如下，遇到第二次了，而且看到网上很多回答并不管用，当然也可能是对应的问题不太相同。

Collecting requests (from -r requirements.txt (line 1))

  Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/requests/
  Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/requests/
  Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/requests/
  Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/requests/
  Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/requests/

解决方法：service docker restart