validate length

prolefeeder.py

@@ -3,7 +3,7 @@ from flask import (Flask, render_template, flash, redirect,
 from flask_bootstrap import Bootstrap
 from flask_wtf import FlaskForm
 from wtforms import DateTimeField, DecimalField, SubmitField
-from wtforms.validators import DataRequired
+from wtforms.validators import DataRequired, NumberRange
 
 from datetime import datetime, timedelta
 
@@ -17,7 +17,8 @@ Bootstrap(app)
 
 class DownloadForm(FlaskForm):
     start_time = DateTimeField('Start time', validators=[DataRequired()])
-    length = DecimalField('Length', validators=[DataRequired()])
+    length = DecimalField('Length', validators=[DataRequired(),
+                                                NumberRange(min=1, max=180)])
     submit = SubmitField('Download')