[DRE-maint] Bug#990471: [meta] support migration from diaspora-installer to diaspora

[Pirate Praveen]

Package: diaspora
Version: 0.7.15.0-2
Severity: important

After installing diaspora-installer and migrating to diaspora package 
following https://wiki.debian.org/Diaspora#Experimental installation 
fails with

Setting up diaspora (0.7.15.0-2) ...
Your bundle only supports platforms [] but your local platform is 
x86_64-linux. Add the current
platform to the lockfile with `bundle lock --add-platform x86_64-linux` 
and try again.
dpkg: error processing package diaspora (--configure):