fix migration system for post-consolidation migrations, better errors

[rphmeier]

No description provided.

[coveralls]

Coverage increased (+0.04%) to 85.21% when pulling b8b3f06 on fix-migrations into 92451ef on master.

[coveralls]

Coverage increased (+0.03%) to 85.206% when pulling b8b3f06 on fix-migrations into 92451ef on master.

[NikVolf]

Can you provide an example of a problem supposed to be solved by introducing this change?

[rphmeier]

sure! before the post-consolidation migrations, there are 5 columns in the database and we start with version 9. The earliest migration the manager can have within it is version 10, which means that the old no_of_columns_at function would always return None and opening the database would fail.

This solves that problem by finding the number of columns before the migrations by asking the first migration how many columns it expects the database to have before it is put into effect.