title: sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unknown database "mydb"
body: <p>I have a problem to use flask_alchemy for my unit test function</p>
  <p>In the production environment I use a postgresql database</p>
  <pre><code>&quot;SQLALCHEMY_DATABASE_URI&quot;: &quot;postgresql://login:passwd@dburl:1234/mydatabase&quot;,
  </code></pre>
  <p>To work with the postgresql schema, in my entity definition i declare a  _<em>table_args</em> to specify a schema</p>
  <pre><code>    class MyTable(Base):
          __tablename__ = 'my_tablename'
          __table_args__ = {'schema': 'mydbschema'}
      
          my_id = Column('my_id', Date, primary_key=True)
  
  ....
  </code></pre>
  <p>But in my unittest i would like to use a memory database</p>
  <pre><code>&quot;SQLALCHEMY_DATABASE_URI&quot;: &quot;sqlite://&quot;,
  </code></pre>
  <p>When i run my function i have this error :</p>
  <pre><code>E   sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unknown database &quot;mydbschema&quot;
  </code></pre>
  <p>Somebody knows a workarround in this case ?</p>