test/functional: retry/Screen: failure instead of error #11173

- Running out of retries, or unexpected screen state should make the
  test FAIL, not ERROR.
- Uses levels to report the location of the caller.
- Improve message with retry-failure (formatting).

Before:

    [ RUN      ] test: 103.53 ms ERR
    test/functional/helpers.lua:388:
    retry() attempts: 1
    test/functional/ui/screen.lua:587: Row 1 did not match.
    Expected:
      |*X^                         |
      |{0:~                        }|
      |{0:~                        }|
      |                         |
    Actual:
      |*^                         |
      |{0:~                        }|
      |{0:~                        }|
      |                         |

    To print the expect() call that would assert the current screen state, use
    screen:snapshot_util(). In case of non-deterministic failures, use
    screen:redraw_debug() to show all intermediate screen states.

    stack traceback:
            test/functional/helpers.lua:388: in function 'retry'
            test/functional/test_spec.lua:24: in function <test/functional/test_spec.lua:23>

After:

    [ RUN      ] test: 105.22 ms FAIL
    test/functional/test_spec.lua:24: stopping after 1 retry() attempts.
    test/functional/test_spec.lua:25: Row 1 did not match.
    Expected:
      |*X^                         |
      |{0:~                        }|
      |{0:~                        }|
      |                         |
    Actual:
      |*^                         |
      |{0:~                        }|
      |{0:~                        }|
      |                         |

    To print the expect() call that would assert the current screen state, use
    screen:snapshot_util(). In case of non-deterministic failures, use
    screen:redraw_debug() to show all intermediate screen states.

    stack traceback:
            test/functional/helpers.lua:389: in function 'retry'
            test/functional/test_spec.lua:24: in function <test/functional/test_spec.lua:23>

0 files changed, 0 insertions, 0 deletions