Spacemacs fails to start with error "Symbol's value as variable is void: \213"

Hi,

I tried to use [spacemacs](http://spacemacs.org/) with flatpak emacs and if I switch to `develop` branch, which is recommended, I'm hitting this issue:

```
Warning (initialization): An error occurred while loading ‘/home/zlopez/.emacs.d/init.el’:

Symbol's value as variable is void: \213

To ensure normal operation, you should investigate and remove the
cause of the error in your initialization file. Start Emacs with
the ‘--debug-init’ option to view a complete error backtrace.
```

This could be related to https://github.com/syl20bnr/spacemacs/issues/11585. According to [discussion](https://github.com/syl20bnr/spacemacs/issues/11585#issuecomment-484531038) this issue is about missing `gnutls`. I looked at `freedesktop.Sdk` runtime and it looks like gnutls is not part of this runtime.

Reproduce the failure with the Spacemacs develop branch and Flatpak Emacs, starting with the reported ~/.emacs.d/init.el warning and Emacs's --debug-init option. Inspect the freedesktop.Sdk runtime for the reported missing gnutls dependency; done means Spacemacs starts without the void-variable error.

Written by the indexing model from the issue text.