For some reason, I have too many versions of pip installed, causing both pip and pip3 to report this error. I have been looking for a solution for a long time without success. Today I suddenly found it after searching again, but it is still ok.
python2 pip solution
pip install aliyun-python-sdk-core==2.3.5 aliyun-python-sdk-rds datetime
#报错
The 'pip==7.1.0' distribution was not found and is required by the application
https://files.pythonhosted.org/packages/07/9d/2af576b8b199c69d839a8dfd6025b6721a18a0b771a051b2b62b3c866d0f/distribute-0.6.10.tar.gz
tar -zxvf distribute-0.6.10.tar.gz
cd distribute-0.6.10
python setup.py install
easy_install pip==7.1.0
pip install aliyun-python-sdk-core==2.3.5 aliyun-python-sdk-rds datetime
python3 solution
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
sudo python3 get-pip.py