Bug#852612: bug severity upgrade?

[Robert Lange]

Is it possible to get an upgrade in severity to grave for this bug (or  
the linked bug #851928)? The fix for this bug is blocked from entering  
testing by another bug that is marked grave:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=853170
Both of (#852612 / #851928) and #853170 cause some set of machines to  
be unbootable, so it seems that they should have the same severity.