I know this is just test code but I would suggest not to use the `%(name)s` notation with SQL. 
If you have variables you want to insert, do it in "runtime" with the `cursor.execute()` function like this:
```python
        cursor.execute("""
INSERT INTO signature_summary_products
(signature_id, product_version_id, product_name,
version_string, report_date, report_count)
VALUES
(%s, %s, 'Firefox',
'9.0', %s, 1)
""", ( signature_id,  other_product_version_id, yesterday)
)
 ```

Also, if you ever do want to use actual string interpolation use the new form using the `{}` style. Like this:
```python
>>> "select * from {table}".format(table='foo')
'select * from foo'
```