old_contents: 
  from . import sqlite
  __all__ = ['sqlite']
  
  try:
  	from . import mysql
  	__all__.append('mysql')
  except ImportError:
  	mysql = None
  
new_contents: 
  # sqlite is always available
  
  from . import sqlite
  __all__ = ['sqlite']
  
  
  # mysql driver depends on MySQLdb
  
  try:
      from . import mysql
  except ImportError:
      mysql = None
  
  __all__.append('mysql')
  
subject: add "mysql" to __all__ unconditionally