Fix system tests for source copies of NVDA

[lukaszgo1]

Link to issue number:

None - Fixes regression introduced in PR #12075

Summary of the issue:

When executing system tests ensuring that NVDA starts and exits correctly we rely on the status of its process i.e. when the process is running NVDA is supposed to be running. While this works well for installed copies source copies are not started directly rather intermediate .bat file is used to start pythonw in a separate process. As a consequence when trying to retrieve status of an NVDA process during tests we get wrong results (the bat file is never running).

Description of how this pull request fixes the issue:

To avoid relying on the state of the process system tests use the NVDA's message window to determine if NVDA is running or not.

Testing strategy:

System tests passes both locally against a source copy and on AppVeyor against a binary one.

Known issues with pull request:

None known

Change log entries:

None needed.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English

[seanbudd]

Thanks @lukaszgo1, looks good to me other than 2 minor changes