Update model and migration script

app/models.py

@@ -130,11 +130,11 @@ class BrandingTypes(db.Model):
     name = db.Column(db.String(255), primary_key=True)
 
 
-class Organisation(db.Model, Versioned):
+class Organisation(db.Model):
     __tablename__ = 'organisation'
     id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     colour = db.Column(db.String(7), nullable=True)
-    logo = db.Column(db.String(255), nullable=True)
+    logo = db.Column(db.String(255), nullable=False)
     name = db.Column(db.String(255), nullable=True)
 
     @classmethod

migrations/versions/0105_change_logo_not_nullable.py

@@ -0,0 +1,27 @@
+"""empty message
+
+Revision ID: 0105_change_logo_not_nullable
+Revises: 0104_more_letter_orgs
+Create Date: 2017-07-06 10:14:35.188404
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '0105_change_logo_not_nullable'
+down_revision = '0104_more_letter_orgs'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+
+def upgrade():
+    op.alter_column('organisation', 'logo',
+               existing_type=sa.VARCHAR(length=255),
+               nullable=False)
+
+
+def downgrade():
+    op.alter_column('organisation', 'logo',
+               existing_type=sa.VARCHAR(length=255),
+               nullable=True)