Remote extract generation timeout results in error with db connection

[spwoodcock]

Describe the bug

  File "/opt/app/projects/project_crud.py", line 531, in <lambda>
    lambda: split_by_sql(
            └ <function split_by_sql at 0x7f0a75496680>

  File "/home/appuser/.local/lib/python3.10/site-packages/fmtm_splitter/splitter.py", line 494, in split_by_sql
    featcol = splitter.splitBySQL(query, db, num_buildings, osm_extract=extract_geojson)
              │        │          │      │   │                          └ {'type': 'FeatureCollection', 'features': [{'type': 'Feature', 'geometry': {'type': 'LineString', 'coordinates': [[-10.791561...
              │        │          │      │   └ 5
              │        │          │      └ <sqlalchemy.orm.session.Session object at 0x7f0a7214bfd0>
              │        │          └ 'DROP TABLE IF EXISTS polygonsnocount;\n-- Create a new polygon layer of splits by lines\n\nCREATE TABLE polygonsnocount AS (...
              │        └ <function FMTMSplitter.splitBySQL at 0x7f0a754964d0>
              └ <fmtm_splitter.splitter.FMTMSplitter object at 0x7f0a72b618d0>
  File "/home/appuser/.local/lib/python3.10/site-packages/fmtm_splitter/splitter.py", line 234, in splitBySQL
    create_tables(conn)
    │             └ <sqlalchemy.pool.base._ConnectionFairy object at 0x7f0a721ea2c0>
    └ <function create_tables at 0x7f0a75495f30>
  File "/home/appuser/.local/lib/python3.10/site-packages/fmtm_splitter/db.py", line 87, in create_tables
    drop_tables(conn)
    │           └ <sqlalchemy.pool.base._ConnectionFairy object at 0x7f0a721ea2c0>
    └ <function drop_tables at 0x7f0a75495fc0>
  File "/home/appuser/.local/lib/python3.10/site-packages/fmtm_splitter/db.py", line 136, in drop_tables
    cur = conn.cursor()
          │    └ <function _ConnectionFairy.cursor at 0x7f0a8a760c10>
          └ <sqlalchemy.pool.base._ConnectionFairy object at 0x7f0a721ea2c0>
  File "/home/appuser/.local/lib/python3.10/site-packages/sqlalchemy/pool/base.py", line 1490, in cursor
    assert self.dbapi_connection is not None
           │    └ <member 'dbapi_connection' of '_ConnectionFairy' objects>
           └ <sqlalchemy.pool.base._ConnectionFairy object at 0x7f0a721ea2c0>

AssertionError: assert self.dbapi_connection is not None

To Reproduce

• Occurs occasionally when the data extract generation / polling times out in FMTM.

Expected behavior

• There should be handling for the self.dbapi_connection.
• It should not error if self.dbapi_connection is not None.