运行安装命令
pip install rqalpha-data
提示错误，并要求升级 pip，升级 pip 后，同样错误仍然存在，如下：
Collecting rqalpha-data
Using cached https://files.pythonhosted.org/packages/7b/c0/3496c1edf9c1ec4a7eaafc714fe62c8794935308c6aa1ba457b45fb8a4aa/rqalpha-data-0.0.7.tar.gz
Complete output from command python setup.py egg_info:
Traceback (most recent call last):
File "", line 1, in
File "/private/var/folders/17/n3ynjfmj41b3c67bgl8y47600000gn/T/pip-install-nshlbh9u/rqalpha-data/setup.py", line 7, in
from pip.req import parse_requirements
ImportError: cannot import name 'parse_requirements'

----------------------------------------

Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/17/n3ynjfmj41b3c67bgl8y47600000gn/T/pip-install-nshlbh9u/rqalpha-data/

查找解决办法，这个页面
https://stackoverflow.com/questions/25192794/no-module-named-pip-req
提到是 pip 版本的问题：

This is happening lately because of a change in pip 10.

The fix is pretty easy. You probably have something like:

from pip.req import parse_requirements
Change that to something like:

try: # for pip >= 10
    from pip._internal.req import parse_requirements
except ImportError: # for pip <= 9.0.3
    from pip.req import parse_requirements

最新的 pip 版本是19.0.1，是不是需要修改部分源码？