Install robotframework and robotframework-ride through pip2 in python2 environment in Centos system

 illustrate:

1. If pip2 install does not add --user, it will report an error of insufficient permissions, so you need to add --user to solve it

 2. If you want to check the installation location after pip2 install, you can use pip2 uninstall, which will list the detailed information of the package to be "uninstalled".