Fix "ImportError: No module named weakref" in Python 2.7

[greyli]

close #2961

[Jamim]

I think it's reasonable to squash the commits.

[immerrr]

Could you please also add backports.shutil_get_terminal_size in the same manner to also fix #2950 ?

[greyli]

@Jamim Thanks for the notice, but I think I did something wrong with Git.

[greyli]

Close in favor of #2967.

[Jamim]

@greyli I believe this article might be helpful:
Git Tools - Rewriting History

[immerrr]

Recovering from a merge with interactive rebase could be painful though.

I would suggest creating a new branch locally (which Grey Li did) and push it to update patch-2 branch on github, roughly smth like git push --force-with-lease origin fix-import-error-on-py-2:patch-2

[techalchemy]

Git captures all activity in the reflog by default so it should be recoverable just by the original hash. Ping me on slack if you have trouble

[greyli]

@Jamim @immerrr @techalchemy Thanks for the tips!