Fix a few obsolete uses of Flask-WTF forms

It seems that in a recent version, Flask-WTF's forms stopped
providing the hidden_tag() method. Instead, FlaskForms provide
that method.

Author: ldionne

lnt/server/ui/regression_views.py

@@ -6,11 +6,11 @@
 from flask import render_template
 from flask import request
 from flask import flash
+import flask_wtf
 from sqlalchemy import desc
 from sqlalchemy.orm.exc import NoResultFound
 from wtforms import SelectMultipleField, StringField, widgets, SelectField
 from wtforms import HiddenField
-from flask_wtf import Form
 from wtforms.validators import DataRequired
 
 from lnt.server.ui.decorators import v4_route
@@ -39,7 +39,7 @@ class MultiCheckboxField(SelectMultipleField):
     option_widget = widgets.CheckboxInput()
 
 
-class TriagePageSelectedForm(Form):
+class TriagePageSelectedForm(flask_wtf.FlaskForm):
     field_changes = MultiCheckboxField("Changes", coerce=int)
     name = StringField('name', validators=[DataRequired()])
 
@@ -125,7 +125,7 @@ def calc_impact(session, ts, fcs):
     return PrecomputedCR(1, 1, True)
 
 
-class MergeRegressionForm(Form):
+class MergeRegressionForm(flask_wtf.FlaskForm):
     regression_checkboxes = MultiCheckboxField("regression_checkboxes",
                                                coerce=int)
 
@@ -251,7 +251,7 @@ def _get_regressions_from_selected_form(session, form, ts):
     return reg_inds, regressions
 
 
-class EditRegressionForm(Form):
+class EditRegressionForm(flask_wtf.FlaskForm):
     title = StringField(u'Title', validators=[DataRequired()])
     bug = StringField(u'Bug', validators=[DataRequired()])
     field_changes = MultiCheckboxField("Changes", coerce=int)

lnt/server/ui/views.py

@@ -9,6 +9,7 @@
 from io import BytesIO
 
 import flask
+import flask_wtf
 import sqlalchemy.sql
 from flask import abort
 from flask import current_app
@@ -18,7 +19,6 @@
 from flask import render_template
 from flask import request, url_for
 from flask import send_file
-from flask_wtf import Form
 from sqlalchemy.orm import joinedload
 from sqlalchemy.orm.exc import NoResultFound
 from wtforms import SelectField, StringField, SubmitField
@@ -584,7 +584,7 @@ def v4_run(id):
     return render_template("v4_run.html", **data)
 
 
-class PromoteOrderToBaseline(Form):
+class PromoteOrderToBaseline(flask_wtf.FlaskForm):
     name = StringField('Name', validators=[DataRequired(), Length(max=32)])
     description = StringField('Description', validators=[Length(max=256)])
     promote = SubmitField('Promote')
@@ -1845,7 +1845,7 @@ def v4_search():
 ]
 
 
-class MatrixOptions(Form):
+class MatrixOptions(flask_wtf.FlaskForm):
     limit = SelectField('Size', choices=MATRIX_LIMITS)