Handling Flask-Reuploaded error when uploading a file with a disallowed filetype or no file

Solution 1
...
from flask_uploads.exceptions import UploadNotAllowed
...

@app.route("/", methods=['GET', 'POST'])
def upload():
    if request.method == 'POST' and 'photo' in request.files:
        try:
            photos.save(request.files['photo'])
            flash("Photo saved successfully.")
            return render_template('upload.html')
        except UploadNotAllowed:
            flash("File type not allowed!")
            return render_template('upload.html')
    return render_template('upload.html')
if request.method == 'POST':
    if form.validate_on_submit() and 'artwork' in request.files:
        art = form.artwork.data
        this_artf = art_f+'/'+str(order_no_art)
        app.config['UPLOADED_IMAGES_DEST'] = this_artf
        images = UploadSet('images', IMAGES)
        configure_uploads(app, images)
app.config['UPLOADED_IMAGES_DEST'] = this_artf
images = UploadSet('images', IMAGES)
configure_uploads(app, images)
Solution 2
from flask_uploads.exceptions import UploadNotAllowed
from flask import flash # make sure to configure secret key for your app
#....

error_files = []
for image in art:
    try:
        images.save(image)
    except flask_uploads.exceptions.UploadNotAllowed as err:
        error_files.append(image.filename)
        continue

flash(error_files, 'error')