Allow server-side panel code on S3

[forman]

The code for server-side panels can now also be loaded from S3. For example:

base_dir: "s3://xcube-testing"

Viewer:
  Augmentation:
    Path: "viewer/extensions"
    Extensions:
      - my_ext.ext

In addition, the xcube test helper module test.s3test has been enhanced to support testing the experimental server-side panels described above:

• added new decorator @s3_test() for individual tests with timeout arg;
• added new context manager s3_test_server() with timeout arg to be used within tests function bodies;
• S3Test, @s3_test(), and s3_test_server() now restore environment variables modified for the Moto S3 test server.

Checklist:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• [ ] New/modified features documented in docs/source/*
• Changes documented in CHANGES.md
• GitHub CI passes
• AppVeyor CI passes
• Test coverage remains or increases (target 100%)

[TejasMorbagal]

Tried to test it on the dev deployment, still doesn't work

[I 2024-11-15 13:53:39,345 xcube] Applying initial configuration...
[W 2024-11-15 13:53:39,348 xcube] Downloading s3://xcube-viewer-app/bc/dev to /tmp/xcube-viewer-aux-utjgj30v
[W 2024-11-15 13:53:39,722 xcube] Temporarily prepending '/tmp/xcube-viewer-aux-utjgj30v' to sys.path
[I 2024-11-15 13:53:39,722 xcube] Loading viewer extension(s) my_viewer_ext.ext
[I 2024-11-15 13:53:39,723 xcube] Restored sys.path
[E 2024-11-15 13:53:39,723 xcube] Internal error: No module named 'my_viewer_ext'
Traceback (most recent call last):
File "/opt/conda/lib/python3.12/site-packages/xcube/cli/main.py", line 87, in main
exit_code = cli.main(args=args, obj=ctx_obj, standalone_mode=False)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/click/core.py", line 1078, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/click/core.py", line 1688, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/click/core.py", line 1434, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/click/core.py", line 783, in invoke
return __callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/xcube/cli/serve.py", line 251, in serve
server = Server(framework, config)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/xcube/server/server.py", line 97, in init
ctx.on_update(None)
File "/opt/conda/lib/python3.12/site-packages/xcube/server/server.py", line 511, in on_update
next_api_ctx.on_update(prev_api_ctx)
File "/opt/conda/lib/python3.12/site-packages/xcube/webapi/viewer/context.py", line 41, in on_update
self.set_extension_context(path, extension_refs)
File "/opt/conda/lib/python3.12/site-packages/xcube/webapi/viewer/context.py", line 76, in set_extension_context
self.ext_ctx = ExtensionContext.load(self.server_ctx, extension_refs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/site-packages/chartlets/extensioncontext.py", line 58, in load
module = importlib.import_module(module_name)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/conda/lib/python3.12/importlib/init.py", line 90, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "", line 1387, in _gcd_import
File "", line 1360, in _find_and_load
File "", line 1324, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'my_viewer_ext'

the my_viewer_ext exists on s3.

[forman]

[W 2024-11-15 13:53:39,348 xcube] Downloading s3://xcube-viewer-app/bc/dev to /tmp/xcube-viewer-aux-utjgj30v
[W 2024-11-15 13:53:39,722 xcube] Temporarily prepending '/tmp/xcube-viewer-aux-utjgj30v' to sys.path

s3://xcube-viewer-app/bc/dev seems to be empty.

[TejasMorbagal]

Tested and it works now!