I am getting this error while doing a `nix-channel --update`. 
```
nix-channel: src/libfetchers/tarball.cc:67: nix::fetchers::DownloadFileResult nix::fetchers::downloadFile(nix::ref<nix::Store>, const string&, const string&, bool, const Headers&): Assertion `request.expectedETag == res.etag' failed.
fish: “nix-channel --update” terminated by signal SIGABRT (Abort)
```
What might be the issue here?