Hopefully just a final followup:
I removed these files:
cd /var/lib/mysql/mysql
rm -f innodb_index_stats.frm
rm -f innodb_index_stats.ibd
rm -f innodb_table_stats.frm
rm -f innodb_table_stats.ibd
rm -f slave_master_info.frm
rm -f slave_master_info.ibd
rm -f slave_relay_log_info.frm
rm -f slave_relay_log_info.ibd
rm -f slave_worker_info.frm
rm -f slave_worker_info.ibd
then I created them again according to
http://dba.stackexchange.com/questions/111616/innodb-error-table-mysql-innodb-table-stats-not-found
I dropped the ecom database, but had to remove the directories manually.
I created the database ecom again and used the datadump to fill all tables.
Sigh, that was a long way to (find and) go!