« cabal new-update » fails on an old « repository »

e.g.:

```
$ cabal new-update

Downloading the latest package lists from:
- stackage-lts-13.9
- hackage.mobilehaskell
- hackage.haskell.org

dieVerbatim: user error (cabal: '/usr/bin/curl' exited with an error:
curl: (7) Failed to connect to hackage.mobilehaskell.org port 443: Connection
refused
)
```

I've since both [1] changed an `https` to `http` and [2] deleted this `repository`:

```
repository hackage.mobilehaskell
url: http://hackage.mobilehaskell.org/
```

and I've tried:

* `cabal new-clean`
* grepping the `~/.cabal/store` for the repository name/url, but didn't find anything.

but the error persists.

how do I modify or remove a repository, and/or how do I delete the cache of known repositories?

thanks.

Start with the repository configuration handling exercised by `cabal new-update`, using the shown `repository hackage.mobilehaskell` block and the attempted `cabal new-clean` command as the reproduction. Trace where configured repositories or their cache are read, then verify that changing or deleting the repository prevents the obsolete URL from being contacted.

Written by the indexing model from the issue text.