SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes
This is probably due to the index limitations. From the MySQL docs: CREATE INDEX Syntax


  Prefix support and lengths of prefixes (where supported) are storage engine dependent. For example, a prefix can be up to 1000 bytes long for MyISAM tables, and 767 bytes for InnoDB tables. 


You probably have a VARCHAR column with length more than 767 or a TEXT column.