Describe needed positions in document ballot mail.

This uses doc.utils.needed_ballot_positions() to calculate what is
 needed.
Fixes #924.
Commit ready to merge.
 - Legacy-Id: 7386

ietf/doc/mails.py

@@ -10,6 +10,7 @@ from django.core.urlresolvers import reverse as urlreverse
 from ietf.utils.mail import send_mail, send_mail_text
 from ietf.ipr.search import iprs_from_docs, related_docs
 from ietf.doc.models import WriteupDocEvent, BallotPositionDocEvent, LastCallDocEvent, DocAlias, ConsensusDocEvent, DocTagName
+from ietf.doc.utils import needed_ballot_positions
 from ietf.person.models import Person
 from ietf.group.models import Group, Role
 
@@ -373,6 +374,10 @@ def generate_issue_ballot_mail(request, doc, ballot):
                                  last_call_expires=last_call_expires,
                                  approval_text=approval_text,
                                  ballot_writeup=ballot_writeup,
+                                 needed_ballot_positions=
+                                   needed_ballot_positions(doc,
+                                     doc.active_ballot().active_ad_positions().values()
+                                   ),
                                  )
                             )
 

ietf/templates/doc/mail/issue_ballot_mail.txt

@@ -17,8 +17,7 @@ Subject: Evaluation: {{ doc.file_tag }} to {{ doc|std_level_prompt }}
 {% for fmt in inactive_ad_positions %}{{ fmt }}
 {% endfor %}{% endif %}
 
-"Yes" or "No-Objection" positions from 2/3 of non-recused ADs, 
-with no "Discuss" positions, are needed for approval.
+{% filter wordwrap:73 %}{{ needed_ballot_positions }}{% endfilter %}
 
 DISCUSSES AND COMMENTS
 ======================