git push fails with remote: error: hook declined to update refs/heads/master

That the remote declined to receive the data is only a side effect of the real problem -- git thinks that it was denied because one of the hooks on the remote end failed with an exit status >0 (you can see what it was in the Ruby traceback). It seems that one of the hooks tries to use rake, and can't find it. This is not a problem with your specific repo, probably. That message is also not from your local computer -- notice that it is prefixed with "remote", it is the remote that is missing rake, so probably only a sysadmin on that side can fix the issue.

I would suggest you contact whoever manages your community git repository.