Comment 6 for bug 1495064

BTW more details on #2/#5, the two involved "migrations" are:

* 'metadataserver/migrations/0015_rename_nodecommissionresult_add_result_type.py' that renames 'metadataserver_nodecommissionresult' to 'metadataserver_noderesult' (and adds a field). This "migration" is the latest metadataserver one in 1.7.6 and 1.8.0.

* 'maasserver/migrations/0121_recompute_storage_size.py' that relies on the renaming done by '0015_rename_nodecommissionresult_add_result_type' but fails since all 'maasserver' "migrations" are done before all 'metadataserver' ones and '0015_rename_nodecommissionresult_add_result_type' is not in 1.5.4.

In all this the last migrations ('maaserver', 'metadataserver') for 1.5.4 are 0074 and 0014, for 1.7.6 are 0120 and 0015, and for 1.8.0 are 0138 and 0015.

I am somewhat perplexed by the log of "migrations" for a clean install of 1.8.0 which does not fail, even if it applies all the metadata server "migrations", including 0015, after all the other ones, including 0121. I guess that 1.8.0 comes with a database schema already updated and that the "migrations" are idempotent.