def doctests():
    """
    >>> d = Database()
    >>> d.execute("create table table1 (name varchar primary key, email varchar not null unique);")
    >>> d.execute("insert into table1 (name, email) values ('sah', 'sah@blackearthgroup.com')")
    >>> d.execute("insert into table1 (name, email) values ('sah', 'sah.harrison@gmail.com')")
    Traceback (most recent call last):
      ...
    sqlite3.IntegrityError: UNIQUE constraint failed: table1.name
    """
