title: Flask migration error when using flask-migrate
body: <p>I can't seem to get <code>Flask</code> to migrate my models. I'm following along with the <a href="https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-iv-database" rel="nofollow noreferrer">Flask Mega-Tutorial series</a>. At the database setup part of the tutorial, I'm just trying to substitute <code>MySQL</code> for <code>SQLite</code> that is used in the tutorial. 
  I followed <code>SQLAlchemy</code>'s instructions for connecting to a <code>MySQL</code> database, and I've included <code>mysqlclient</code> in my pipfile.
  But when I run: </p>
  
  <pre><code>flask db init
  flask db migrate
  </code></pre>
  
  <p>I get the following:</p>
  
  <pre><code>INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
  INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
  ERROR [root] Error: Can't locate revision identified by '7bb962b87f19'
  </code></pre>
  
  <p>I've tried deleting the migrations folder, and I've deleted the environment and recreated to see if that would fix anything. But it keeps saying it <code>can't locate revision</code>. I thought maybe it did something with the database, I've read other solutions saying you have to flush the database. But, there aren't any tables created or any schemas in the database.</p>
  
  <p>Other info:</p>
  
  <pre><code>DATABASE_URL="mysql://root:mypassword@localhost/flask_tutorial"
  </code></pre>
  
  <p><code>SQLite</code> database runs fine and makes the migrations. So it must be something I've done with the mysql setup.</p>
  
  <p>Any suggestions or ideas that may lead me in the right direction would be greatly appreciated.</p>