This is not about how hard or easy it is to move from GitHub. What scares me is that it is increasingly hard to participate in the open source/free software community without using GitHub, and it is increasingly hard to find contributors for your own project if you are not willing to host it there.
The programming community became globally dependent on a single commercial company. Using GitHub would mean contributing to that dependence and monopolization even more.
It's not just about moving data from one provider to another. GitHub is not simply a hosting service, it's a large centralized social network, and the cost of switching from it includes reduced project visibility and disconnection from the community.
These may be issues for smaller projects, but I don't feel that either visibility or community is a problem for a project like Python. They have the luxury of going wherever they want and people will follow.
