This is an important bugfix and should be tagged.

• Check the language code exists before we search for it.
• Add the missing InstallSignature role from the backend auto-detection.
• Disable repos that are not contactable at backend start.
• Don't allow double clicking SRPM and fix the cryptic message.
• Fixes #529349, #531105, #530945, #531306 and #530264

I've tested this, and 5 or 6 people have tested this build in the bugs linked above. This needs to be tagged for importing the livna key to work at first boot and to avoid spamming the user for fonts that are never going to exist.

Thanks.