issue2551251 - migrate pbkdf2 passwords if more rounds configured migrate/re-encrypt PBKDF2 password if stored password used a smaller number of rounds than set in password_pbkdf2_default_rounds. Also increase fallback number of rounds (when not set in config) to 2,000,000.

try:
    # Python 3+
    from ssl import SSLError
except (ImportError, AttributeError):
    # Python 2.5-2.7
    from socket import sslerror as SSLError