用pip安装tornado库：
python -m pip install tornado
出现问题一： Could not fetch URL https://pypi.org/simple/twisted/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/twisted/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping
解决办法：python -m pip install tornado --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org
即在库名后＋ --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org
出现问题二：pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out.
解决办法：python -m pip install --default-timeout=100 tornado --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org