fix: resolve null VoteTS columns via migration

Somehow, many aur.al records of PackageVotes do not have a valid VoteTS
value. This migration fixes that issue by setting all null VoteTS
columns to the epoch timestamp.

Signed-off-by: Kevin Morris <kevr@0cost.org>

migrations/versions/d64e5571bc8d_fix_pkgvote_votets.py

@@ -0,0 +1,37 @@
+"""fix pkgvote votets
+
+Revision ID: d64e5571bc8d
+Revises: be7adae47ac3
+Create Date: 2022-02-18 12:47:05.322766
+
+"""
+from datetime import datetime
+
+import sqlalchemy as sa
+
+from alembic import op
+
+from aurweb import db
+from aurweb.models import PackageVote
+
+# revision identifiers, used by Alembic.
+revision = 'd64e5571bc8d'
+down_revision = 'be7adae47ac3'
+branch_labels = None
+depends_on = None
+
+table = PackageVote.__tablename__
+column = 'VoteTS'
+epoch = datetime(1970, 1, 1)
+
+
+def upgrade():
+    with db.begin():
+        records = db.query(PackageVote).filter(PackageVote.VoteTS.is_(None))
+        for record in records:
+            record.VoteTS = epoch.timestamp()
+    op.alter_column(table, column, existing_type=sa.BIGINT(), nullable=False)
+
+
+def downgrade():
+    op.alter_column(table, column, existing_type=sa.BIGINT(), nullable=True)