Alias our subqueries to appease the MySQL beast

data/model/storage.py

@@ -226,12 +226,14 @@ def lookup_repo_storages_by_content_checksum(repo, checksums):
   # to use a union to select just one storage with each checksum
   queries = []
 
-  for checksum in set(checksums):
+  for counter, checksum in enumerate(set(checksums)):
+    query_alias = 'q{0}'.format(counter)
     candidate_subq = (ImageStorage
                       .select(ImageStorage.id, ImageStorage.content_checksum)
                       .join(Image)
                       .where(Image.repository == repo, ImageStorage.content_checksum == checksum)
-                      .limit(1))
+                      .limit(1)
+                      .alias(query_alias))
     queries.append(ImageStorage
                    .select(SQL('*'))
                    .from_(candidate_subq))