There is now a bug fix release 3.7.1 of Nominatim available.
This release fixes some compatibility issues with older versions of Python which meant that Nominatim could not be used on Ubuntu 18.04. With the new release the code now works with all Python versions >= 3.5 as described in the documentation.
The release also fixes an issue with index naming which prevented one of the indexes on the TIGER tables to be created. If you already have installed a new database using the 3.7.0 release, you need to add this index manually:
CREATE UNIQUE INDEX idx_location_property_tiger_place_id ON location_property_tiger_import (place_id);
If you plan to do a new installation of Nominatim, you should make sure to switch to the new version. Existing installations can skip this release.