WTForms: Install 'email_validator' for email validation support

If you take a look at wtforms/validators.py file in line 9:

import email_validator

Just install the package:

pip install email_validator

If you want it installed with wtforms:

pip install wtforms[email]

From WTForms 2.3.0 version, the email validation is handled by an external library called email-validator (PR #429). If you want to enable email validation support, you either need to install WTForms with extra requires email:

$ pip install wtforms[email]

Or you can install email-validator directly:

$ pip install email-validator

Or you can back to the old version of WTForms:

$ pip install wtforms==2.2.1

P.S. If you are using Flask-WTF, except for install email-validator directly, you can also use email extra (if PR #423 got merged) in the next release (> 0.14.3).

Try install

pip install email-validator

I had the same problem with the latest updates, tried to install email_validator and flask-validator and continued with this exception. Solved by adding in requirements.txt the following line: email-validator == 1.0.5 as suggested [here].(https://github.com/alphagov/notifications-admin/commit/5ce2906c5aa6d16)

Actually wtforms[email]==2.3.1 is what I need.