Get SQLite error using heroku db:push when I'm using PostgreSQL as development db

I was having problems pushing data from my development db to Heroku. I decided to switch to PostgreSQL as my development db and have updated
database.yml and removed the sqlite gem from the gemfiles.

The app runs fine against PostgreSQL but when I try to run the command:

heroku db:push

I get an SQLite error which is puzzling because there is no reference to sqlite in my project:

 !    Taps Load Error: cannot load such file -- sqlite3
 !    You may need to install or update the taps gem to use db commands.
 !    On most systems this will be:
 !    sudo gem install taps

Please show yor config/database.yml