Site crashed when updating to 4.0.0-alpha6

There is no upgrade path from 3 to 4.

WORK AROUND:

I had a similar issue with "computed_integer."

Run drush cdel on items that had the computed_integer type
Run drush updatedb to have computed_field_ui enabled

I was able to go back to the content type and add the field back
On export what was computed_integer in the old config was integer.

I changed the module I created by changing the field type from computed_integer to integer, Used drush config-import to re-import just what was effected.

I just wanted to note that I needed to run drush cdel on all configs that had the old field. I couldn't edit it either. It would import because of the error in other configs.

I hope this helps someone else