Use sanitised pdfs for sending and handle invalid pdfs, details below:

- pass new, sanitised pdf for sending
- move invalid pdfs to a newly created bucket
- set status fro notifications that failed pdf validation to a new status validation-failed
- adjust existing tests

migrations/versions/0238_add_validation_failed.py

@@ -0,0 +1,28 @@
+"""
+
+Revision ID: 0238_add_validation_failed
+Revises: 0237_add_filename_to_dvla_org
+Create Date: 2018-09-03 11:24:58.773824
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '0238_add_validation_failed'
+down_revision = '0237_add_filename_to_dvla_org'
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.execute("INSERT INTO notification_status_types (name) VALUES ('validation-failed')")
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.execute("UPDATE notifications SET notification_status = 'permanent-failure' WHERE notification_status = 'validation-failed'")
+    op.execute("UPDATE notification_history SET notification_status = 'permanent-failure' WHERE notification_status = 'validation-failed'")
+
+    op.execute("DELETE FROM notification_status_types WHERE name = 'validation-failed'")
+    # ### end Alembic commands ###