Update EmailBranding.name to be not null and unique.

Needed to update old migration scripts so that the email_branding name is not null when creating the test dbs.
This should no affect the migrations elsewhere.

migrations/versions/0093_data_gov_uk.py

@@ -22,7 +22,7 @@ def upgrade():
         '{}',
         '',
         'data_gov_uk_x2.png',
-        ''
+        'data gov.uk'
     )""".format(DATA_GOV_UK_ID))
 
 

migrations/versions/0099_tfl_dar.py

@@ -22,7 +22,7 @@ def upgrade():
         '{}',
         '',
         'tfl_dar_x2.png',
-        ''
+        'tfl'
     )""".format(TFL_DAR_ID))
 
 

migrations/versions/0101_een_logo.py

@@ -20,7 +20,7 @@ def upgrade():
         '{}',
         '',
         'een_x2.png',
-        ''
+        'een'
     )""".format(ENTERPRISE_EUROPE_NETWORK_ID))
 
 

migrations/versions/0286_add_unique_email_name.py

@@ -0,0 +1,26 @@
+"""
+
+Revision ID: 0286_add_unique_email_name
+Revises: 0285_default_org_branding
+Create Date: 2019-04-09 13:01:13.892249
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = '0286_add_unique_email_name'
+down_revision = '0285_default_org_branding'
+
+
+def upgrade():
+    op.alter_column('email_branding', 'name',
+                    existing_type=sa.VARCHAR(length=255),
+                    nullable=False)
+    op.create_unique_constraint('uq_email_branding_name', 'email_branding', ['name'])
+
+
+def downgrade():
+    op.drop_constraint('uq_email_branding_name', 'email_branding', type_='unique')
+    op.alter_column('email_branding', 'name',
+                    existing_type=sa.VARCHAR(length=255),
+                    nullable=True)