from flask_wtf import Form
from wtforms import StringField, PasswordField
from wtforms.validators import DataRequired, Email


class Login(Form):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField
from wtforms.validators import DataRequired, Email


class Login(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])

Change deprecated flask_wtf.Form with flask_wtf.FlaskForm