Don't remove arch:all binaries when migrating *pu binNMUs

As part of a migration, we remove all the existing binaries built by
the source (possibly on a particular architecture) from testing; this
includes architecture-independent binary packages. However, when a
binNMU is in *pu, only the arch-dependent binary pakcages are present.

As a result, after the migration the architecture-independent packages
are no longer present in testing. This usually isn't a practical
problem, as dak will re-add them when it generates the packages files.

It is, however, wrong and will break if a source migration is tempted
during the same run as (and after) the *pu binary migration happened.

The simple fix is to not remove the architecture-independent packages
when performing such migrations.

Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>

britney.py

@@ -1894,7 +1894,17 @@ class Britney(object):
                 for p in ( bin for bin in bins if bin not in smoothbins ):
                     binary, parch = p.split("/")
                     version = binaries_t[parch][0][binary][VERSION]
-                    rms.add((binary, version, parch))
+                    # if this is a binary migration from *pu, only the arch:any
+                    # packages will be present. ideally dak would also populate
+                    # the arch-indep packages, but as that's not the case we
+                    # must keep them around; they will not be re-added by the
+                    # migration so will end up missing from testing
+                    if migration_architecture != 'source' and \
+                         suite != 'unstable' and \
+                         binaries_t[parch][0][binary][ARCHITECTURE] == 'all':
+                        continue
+                    else:    
+                        rms.add((binary, version, parch))
 
         # single binary removal; used for clearing up after smooth
         # updates but not supported as a manual hint