Do proper downgrades to reset the database

Somehow the table for the alembic migrations was not dropped before, leading to an inconsistent state

ki/test/ApiTest.py

@@ -31,7 +31,8 @@ class ApiTest(unittest.TestCase):
 
     def tearDown(self):
         with app.app_context():
-            db.drop_all()
+            config = migrate.get_config()
+            command.downgrade(config, "base")
             db.engine.dispose()
 
     def login(self, username, password):

migrations/versions/b5023977cbda_extend_skill_length_to_50_chars.py

@@ -22,3 +22,10 @@ def upgrade():
                 existing_type=sa.VARCHAR(length=25),
                 type_=sa.String(length=50),
                 existing_nullable=False)
+
+def downgrade():
+    with op.batch_alter_table("skill") as batch_op:
+        batch_op.alter_column('name',
+                existing_type=sa.String(length=50),
+                type_=sa.VARCHAR(length=25),
+                existing_nullable=False)