`fcntl` package only works on Linux/Unix systems

The state/cache file writing utility that I wrote a few months back uses the fcntl package that comes with base Python to handle file locking. It turns out that this package is only available on Unix/Linux systems and that relying on it has broken support for Geomag-Algorithms on Windows. Right now, if a user installs geomag-algorithms in a Windows environment then tries to run anything that relies on Util.py, e.g.: geomag.py, it will halt with a No module named 'fcntl' error.

File locking is fairly important for state/cache files. I found a couple of possible 'fixes' online:

1. Add in OS-dependent code that uses win32api instead of fcntl if the OS is Windows-based.
2. Use a third-party package such as portalocker. This would mean that we would have to officially add a new package requirement for users.

assigned to @bgeels

Tagging @awernle @erigler @swilbur.

@awernle had a third idea for a fix, we could include an os-check that simply disables the file lock calls on Windows, or put any fcntl calls inside of a try statement. I like this idea because it's probably fairly simple to implement, doesn't add new dependencies, and we don't expect to ever have the full real-time processing pipeline running on Windows.

changed the description

changed the description

mentioned in merge request !345 (merged)

added Bug label