Postgres error upgrading from v2 to v3

I’m seeing the following and am not sure what’s going on when trying to upgrade from v2 to v3.

[2021-06-10 14:20:28,426][PID:1][INFO][root] Generating grammar tables from /usr/lib/python2.7/lib2to3/Grammar.txt
[2021-06-10 14:20:28,456][PID:1][INFO][root] Generating grammar tables from /usr/lib/python2.7/lib2to3/PatternGrammar.txt
Traceback (most recent call last):
  File "/app/manage.py", line 9, in <module>
    manager()
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 345, in main
    return AppGroup.main(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 229, in decorator
    return __ctx.invoke(f, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask_migrate/cli.py", line 132, in upgrade
    _upgrade(directory, revision, sql, tag, x_arg)
  File "/usr/local/lib/python2.7/dist-packages/flask_migrate/__init__.py", line 239, in upgrade
    command.upgrade(config, revision, sql=sql, tag=tag)
  File "/usr/local/lib/python2.7/dist-packages/alembic/command.py", line 254, in upgrade
    script.run_env()
  File "/usr/local/lib/python2.7/dist-packages/alembic/script/base.py", line 425, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/usr/local/lib/python2.7/dist-packages/alembic/util/pyfiles.py", line 81, in load_python_file
    module = load_module_py(module_id, path)
  File "/usr/local/lib/python2.7/dist-packages/alembic/util/compat.py", line 141, in load_module_py
    mod = imp.load_source(module_id, path, fp)
  File "migrations/env.py", line 87, in <module>
    run_migrations_online()
  File "migrations/env.py", line 70, in run_migrations_online
    poolclass=pool.NullPool)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/__init__.py", line 428, in engine_from_config
    return create_engine(url, **options)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/__init__.py", line 387, in create_engine
    return strategy.create(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/strategies.py", line 50, in create
    u = url.make_url(name_or_url)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 194, in make_url
    return _parse_rfc1738_args(name_or_url)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 240, in _parse_rfc1738_args
    return URL(name, **components)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 60, in __init__
    self.port = int(port)
ValueError: invalid literal for int() with base 10: 'postgresql:'

This looks like a configuration mismatch somewhere. Python is trying to cast the string literal postgresql into an integer. Are you certain your postgres connection string is in the right format?