Try to remove old libs during hint run

Attempt the removal of the old libraries from smooth updates during every hint
run. In some cases, the removal needs to happen during the hint run for the
hint to succeed.

Signed-off-by: Ivo De Decker <ivodd@debian.org>

britney.py

@@ -1888,7 +1888,7 @@ class Britney(object):
 
         return (is_accepted, nuninst_after, arch)
 
-    def iter_packages(self, packages, selected, nuninst=None, parent_transaction=None):
+    def iter_packages(self, packages, selected, nuninst=None, parent_transaction=None, try_removals=True):
         """Iter on the list of actions and apply them one-by-one
 
         This method applies the changes from `packages` to testing, checking the uninstallability
@@ -1989,6 +1989,18 @@ class Britney(object):
                         else:
                             maybe_rescheduled_packages.append(comp[0])
 
+        if try_removals and self.options.smooth_updates:
+            self.logger.info("> Removing old packages left in the target suite from smooth updates")
+            removals = old_libraries(self.suite_info, self.options.outofsync_arches)
+            if removals:
+                output_logger.info("Removing packages left in the target suite for smooth updates (%d):", len(removals))
+                log_and_format_old_libraries(self.output_logger, removals)
+                (nuninst_last_accepted, extra) = self.iter_packages(removals,
+                                                                    selected,
+                                                                    nuninst=nuninst_last_accepted,
+                                                                    parent_transaction=parent_transaction,
+                                                                    try_removals=False)
+
         output_logger.info(" finish: [%s]", ",".join(x.uvname for x in selected))
         output_logger.info("endloop: %s", self.eval_nuninst(self.nuninst_orig))
         output_logger.info("    now: %s", self.eval_nuninst(nuninst_last_accepted))