No graceful error message when email authentication fails

[timobrembeck]

Describe the Bug

When the email credentials in the config are not working, all functions which involve sending emails are not failing gracefully, but showing an internal server error instead.

Steps to Reproduce

1. Input wrong email config
2. Resend e.g. an invitation link
3. See error

Expected Behavior

A nice readable error message should be shown which explains the reason

Actual Behavior

An internal server error occurs

Additional Information

Traceback

Feb 01 09:57:40 ERROR   django.request - 500 Internal Server Error: /lkgoerlitz/users/1264/resend-activation-link/
Traceback (most recent call last):
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
  response = get_response(request)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/handlers/base.py", line 181, in _get_response
  response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/views/decorators/http.py", line 40, in inner
  return func(request, *args, **kwargs)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/contrib/auth/decorators.py", line 21, in _wrapped_view
  return view_func(request, *args, **kwargs)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/integreat_cms/cms/views/users/region_user_actions.py", line 86, in resend_activation_link_region
  send_welcome_mail(request, user, activation=True)
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/integreat_cms/cms/utils/welcome_mail_utils.py", line 57, in send_welcome_mail
  send_mail(
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/integreat_cms/cms/utils/email_utils.py", line 73, in send_mail
  email.send()
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/mail/message.py", line 284, in send
  return self.get_connection(fail_silently).send_messages([self])
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/mail/backends/smtp.py", line 102, in send_messages
  new_conn_created = self.open()
File "/opt/integreat-cms/.venv/lib/python3.9/site-packages/django/core/mail/backends/smtp.py", line 69, in open
  self.connection.login(self.username, self.password)
File "/usr/lib/python3.9/smtplib.py", line 734, in login
  raise last_exception
File "/usr/lib/python3.9/smtplib.py", line 723, in login
  (code, resp) = self.auth(
File "/usr/lib/python3.9/smtplib.py", line 646, in auth
  raise SMTPAuthenticationError(code, resp)
smtplib.SMTPAuthenticationError: (534, b'5.7.9 Application-specific password required. Learn more at\n5.7.9  https://support.google.com/mail/?p=InvalidSecondFactor y6-xxx.34 - gsmtp')