Alembic: Include constraint to reject strings with character
<p>I have a table that looks like this</p>

<pre><code>&gt; select * from mytable
  id        value
0  1  hello world
1  2  hello_world
2  3  hello+world
</code></pre>

<p>I'm trying to impose an alembic check constraint, where values in <code>value</code> cannot have the <code>:</code> character. How would I do this using an <code>alembic.op</code> object? What are the <code>upgrade()</code> and <code>downgrade()</code> functions?</p>

<p>Edit: The DB I'm using is Mysql.</p>