[Pip command error] Solve the problem of sys.stderr.write(f"ERROR: {exc}") after ubuntu16.04 upgrade pip

Obtain the repair file get-pip.py¶

1. Access to get repaired files
2. Find the download link of the corresponding version file, such as python3.5,https://bootstrap.pypa.io/pip/3.5/get-pip.py
3. Use wget to download, wget https://bootstrap.pypa.io/pip/3.5/get-pip.py
4. Use the corresponding version of python to execute the file, python3.5 get-pip.py