Anaconda is failing to load a repository because it is sending "$releasever" and "$basearch" instead of interpreting these as variables. I do not recall having this problem in previous releases. 

I am installing Fedora 18 Beta (with anaconda 18.29.2).

I tried the following series of repo lines:

1) The repo:

repo --name=fedora-updates-testing --baseurl=http://mirrors.cs.byu.edu/fedora/updates/testing/$releasever/$basearch

failed to load in anaconda, and the http server gave the error:

File does not exist: /mirrors/fedora/updates/testing/$releasever

2) The repo:

repo --name=fedora-updates-testing --baseurl=http://mirrors.cs.byu.edu/fedora/updates/testing/18/$basearch

failed to load in anaconda, and the http server gave the error:

File does not exist: /mirrors/fedora/updates/testing/18/$basearch

3) Finally, the repo:

repo --name=fedora-updates-testing --baseurl=http://mirrors.cs.byu.edu/fedora/updates/testing/18/x86_64

worked without any errors.