unable to differentiate internal AssertionError from type errors by exit code

[cburroughs]

Per #6003 "in case of a crash, bad arguments, and other non-standard conditions" should result in an exit code of 2, but currently on AssertionError mypy returns 1 which makes it impossible to differentiate from type errors.

#16214 contains a current reproduction case that throw an AssertionError.

$ tox -e lint
...
Traceback (most recent call last):
  File "/home/ecsb/src/o/qiskit-serverless/client/.tox/lint/bin/mypy", line 7, in <module>
    sys.exit(console_entry())
             ^^^^^^^^^^^^^^^
  File "/home/ecsb/src/o/qiskit-serverless/client/.tox/lint/lib/python3.12/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "mypy/main.py", line 144, in main
  File "mypy/main.py", line 219, in run_build
  File "mypy/build.py", line 222, in build
  File "mypy/build.py", line 301, in _build
  File "mypy/build.py", line 2952, in dispatch
  File "mypy/build.py", line 3347, in process_graph
  File "mypy/build.py", line 925, in wait_for_done
  File "mypy/build.py", line 3455, in process_stale_scc
  File "mypy/build.py", line 3415, in process_fresh_modules
  File "mypy/build.py", line 2135, in fix_cross_refs
  File "mypy/fixup.py", line 53, in fixup_module
  File "mypy/fixup.py", line 131, in visit_symbol_table
  File "mypy/lookup.py", line 33, in lookup_fully_qualified
AssertionError: Cannot find module for google
lint: exit 1 (25.06 seconds) /home/ecsb/src/o/qiskit-serverless/client> mypy --install-types --non-interactive . pid=25623
  lint: FAIL code 1 (193.29=setup[152.55]+cmd[0.88,14.80,25.06] seconds)
  evaluation failed :( (193.31 seconds)