Improve loader robustness

[sefgit]

What does this implement/fix? Explain your changes.

Ignore and print loader error and proceed with loading if possible.

There are cases where
"import " in python failed even when clr.AddReference() succeeded, especially when loading "manipulated (probably protected/obfuscated)" C# DLL.

Does this close any currently open issues?

unknown

Any other comments?

Checklist

Check all those that are applicable and complete.

• Make sure to include one or more tests for your change
• If an enhancement PR, please create docs and at best an example
• Ensure you have signed the .NET Foundation CLA
• Add yourself to AUTHORS
• Updated the CHANGELOG

[filmor]

Can you give an example and a testcase for this? If we fail to load types, I'd rather have clr.AddReference error out entirely, and it should certainly not write to stderr.

[sefgit]

Can you give an example and a testcase for this? If we fail to load types, I'd rather have clr.AddReference error out entirely, and it should certainly not write to stderr.

There is no error in calling clr.AddReference().
It's just not possible to call "import " afterwards.
I can't share the dll here publicly but I could provide you its URL thru private message if possible.

[lostmsu]

Console is not a proper way to report errors. Either AddReference should throw or (if that can't be allowed due to backward compatibility concerns if it would fail too often) we should provide a generic DLL loading error handler (e.g. event OnLoadError). Dumping such errors to Debug.WriteLine or Python's warning module (undesirable due to new dependency) would also be acceptable, but a generic handler would still be needed.

[filmor]

There are direct C-API functions to issue warnings: https://docs.python.org/3/c-api/exceptions.html#issuing-warnings

[sefgit]

A verbose flag to enable/disable warning/error console print would be an alternative
Silent failure is totally confusing amd desperating to handle with.
Maybe:
clr.VERBOSE = True
or even introduce verbose level ?