Make 'free' column nullable for now

Author: Aaron Suarez

migrations/versions/fc34137ad3ba_.py

@@ -19,7 +19,7 @@
 
 def upgrade():
     # ### commands auto generated by Alembic - please adjust! ###
-    op.alter_column('resource', 'paid', new_column_name='free', existing_type=sa.Boolean, nullable=False)
+    op.alter_column('resource', 'paid', new_column_name='free', existing_type=sa.Boolean, nullable=True)
     # ### end Alembic commands ###