Github recently changed a compensation in their Trees API and as a result have broken repository.write().

As you can see from the documentation the base_tree argument is supposed to be a tree object sha. This module is using a commit sha. The Github API used to compensate by detecting this invalid commit sha and fetching the tree sha for it in the background but stopped this behaviour in the last four days, throwing an API exception now.

The Commits API can be used to get a tree object sha from a commit.