Confusing heredoc message

While adding bashate to openstack/openstack-ansible, we found that bashate emits:

     E012: heredoc did not end before EOF: ' string=$(python <<EOF'

From https://github.com/openstack/openstack-ansible/blob/ff4cd964c8bd1afd6dc9ce8df742cc0860adff2b/playbooks/roles/os_tempest/templates/openstack_tempest_gate.sh.j2#L107 (reproduced generically below)

     foo=$(cmd <<HEREDOC
     some text
     in a heredoc
     HEREDOC)

It does accept the following:

     foo=$(cmd <<HEREDOC
     some text
     in a heredoc
     HEREDOC
     )

It might be better to provide a better error message if the former is against bashate's style guidelines. That said this seems like a bug that it's missing this and providing that error message.