Bug#1056891: Severity / marking of "uses cython3-legacy" bugs

[Rebecca N. Palmer]

pandas and statsmodels are currently using cython3-legacy.  I left their 
cython 3.0 bugs open when I made this change, as I do want to actually 
switch them to cython 3.x at some point.

These bugs have now been raised to RC.  Is this an intentional attempt 
to remove cython3-legacy (which seems unlikely as there is no such bug 
on cython3-legacy itself), or have they been mistaken for packages that 
still depend on plain cython3 but don't build with cython3 3.x (which 
would be an active FTBFS and hence RC)?

If the second, how should such bugs be marked to make them less 
confusing?  Is removing the usertag enough?