lib/buildstats: Improve error message

Just stating the recipe counts are different isn't helpful, showing
the differences makes it much easier to understand what changed.

(From OE-Core rev: 1d84b782e3af6f0e6922d72895c905877cc33739)

(From OE-Core rev: 047fd7cf6fc2a3d5d170241f5cc5b61b8d9d8522)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/buildstats.py

@@ -263,7 +263,7 @@ class BuildStats(dict):
         """Aggregate other buildstats into this"""
         if set(self.keys()) != set(buildstats.keys()):
             raise ValueError("Refusing to aggregate buildstats, set of "
-                             "recipes is different")
+                             "recipes is different: %s" % (set(self.keys()) ^ set(buildstats.keys())))
         for pkg, data in buildstats.items():
             self[pkg].aggregate(data)