Fix the unique constraint migration

As the unique constrain is created on index and not on column we need to
remove the index first and recreate it without the unique constrain.

Signed-off-by: Michal Konecny <[email protected]>

anitya/db/migrations/versions/ebc827e80373_remove_unique_attribute_from_username.py

@@ -15,12 +15,16 @@
 def upgrade():
     """Alembic migration."""
     # ### commands auto generated by Alembic - please adjust! ###
-    op.drop_constraint("ix_users_username", "users", type_="unique")
+    # Remove the index and recreate it as there is no way to remove just the unique
+    # constrain from index
+    op.drop_index("ix_users_username", "users")
+    op.create_index("ix_users_username", "users", ["username"])
     # ### end Alembic commands ###
 
 
 def downgrade():
     """Downgrade migration."""
     # ### commands auto generated by Alembic - please adjust! ###
-    op.create_unique_constraint("ix_users_username", "users", ["username"])
+    op.drop_index("ix_users_username", "users")
+    op.create_index(op.f("ix_users_username"), "users", ["username"], unique=True)
     # ### end Alembic commands ###