There is a breaking change in itsdangnerous 1.1 (released on Oct 26, 2018). Namely, there is no SigningAlgorithm anymore, which is used by bitcoinaverage PIP lib (_base_client.py).
Users can install an older version (itsdangerous==0.24 for instance) and that would fix the problem. However, this needs to be fixed in the library as well.
Cheers!