def link_user(self, enterprise_customer, user_email):
try:<EOL><INDENT>existing_user = User.objects.get(email=user_email)<EOL>self.get_or_create(enterprise_customer=enterprise_customer, user_id=existing_user.id)<EOL><DEDENT>except User.DoesNotExist:<EOL><INDENT>PendingEnterpriseCustomerUser.objects.get_or_create(enterprise_customer=enterprise_customer,<EOL>user_email=user_email)<EOL><DEDENT>
Link user email to Enterprise Customer.

If :class:`django.contrib.auth.models.User` instance with specified email does not exist,
:class:`.PendingEnterpriseCustomerUser` instance is created instead.